I have a voltage source of 12V but a light that only burns at 5V. The lamp works on 18 mA. Calculate the resistance that you EXTRA have to include in this series connection.

Answers

Answer 1

Answer:

The resistance that will provide this potential drop is 388.89 ohms.

Explanation:

Given;

Voltage source, E = 12 V

Voltage rating of the lamp, V = 5 V

Current through the lamp, I = 18 mA

Extra voltage or potential drop = 12 V - 5 V = 7 V

The resistance that will provide this potential drop (7 V) is calculated as follows:

[tex]R = \frac{V}{I} = \frac{7 \ V}{18 \times 10^{-3} A} \ = 388.89 \ ohms[/tex]

Therefore, the resistance that will provide this potential drop is 388.89 ohms.


Related Questions

6th grade science I mark as brainliest (can someone answer my other question like this?)

Answers

Answer:A: July

B: July and august

C:true

Explanation:

Question 6
2 pts
Jenny loves puffed rice cereal. As she is pouring the cereal, two little pieces of cereal each with
equal charges of 1.85 x10-18 coulombs fall into the bowl 0.025 meters apart. Use Coulomb's Law
to find the electrostatic force between them. (Remember, Coulomb's constant is 8.99 x10
N*m²/C2)
4.9 x 10-23 N
6.2 x 10-15 N
9.0 x 10-3N
2.5 x 10-23 N

Answers

Answer:

4.9 x 10-23 N

Explanation:

I took the test

Describe how the boiling point of water on top of a mountain would be different from its boiling point at sea level.

Answers

Answer:

At elevated altitudes, any cooking that involves boiling or steaming generally requires compensation for lower temperatures because the boiling point of water is lower at higher altitudes due to the decreased atmospheric pressure.

Explanation:

Answer:

The Lower the air pressure the lower the boiling point.

Why could the beam of particles not have a neutral charge?

Answers

Answer:

The positive and negative charges balance each other. Overall, the atom is uncharged (neutral). However, if something happens to make an atom lose or gain an electron then the atom will no longer be neutral. An atom that gains or loses an electron becomes an ion.

Explanation:

I think this is the answer : D

(PLEASE) You go sledding down a hill and are traveling toward the east. At 0s, your velocity is 0m/s. At 5s, your velocity is 30m/s. Calculate your acceleration.

Answers

Answer:

your acceleration is 6 m/s²

Explanation:

Given;

initial velocity, u = 0

initial time, t₀ = 0

final velocity, v = 30 m/s

final time, t = 5 s

The acceleration of is calculated as follows;

[tex]a = \frac{v-u}{t_1-t_0} \\\\a = \frac{30-0}{5-0} \\\\a =\frac{30}{5} \\\\a = 6 \ m/s^2[/tex]

Therefore, your acceleration is 6 m/s²

Could I get help on this question please . My parents won’t help me /:

Answers

Answer:

Tarzan will be moving at 7.4 m/s.

Explanation:

From the question given above, the following data were obtained:

Height (h) of cliff = 2.8 m

Initial velocity (u) = 0 m/s

Final velocity (v) =?

NOTE: Acceleration due to gravity (g) = 9.8 m/s²

Finally, we shall determine how fast (i.e final velocity) Tarzan will be moving at the bottom. This can be obtained as follow:

v² = u² + 2gh

v² = 0² + (2 × 9.8 × 2.8)

v² = 0 + 54.88

v² = 54.88

Take the square root of both side

v = √54.88

v = 7.4 m/s

Therefore, Tarzan will be moving at 7.4 m/s at the bottom.

WILL GIVE BRAINLIEST

Lucas is carrying his rock collection into class. He carries 30 pounds of rare rocks 15 feet into Classroom 6. It takes him
3 minutes to get them into the classroom What is Lucas's speed and level of work? Be sure to show your work with
equations as part of your answer.

Answers

Answer:

10 and 5

Explanation:

Answer:

It is given that,

Force, F = 30 pounds = 133.4 N

Distance, d = 15 feet = 4.572 m

Time taken, t = 3 minutes = 180 seconds

Lucas's speed is given by the ratio of total displacement divided by total time taken. It is given by :

s = 0.0254 m/s

So, her speed is 0.0254 m/s.

Work done, W = F . d

W = 133.4 N × 4.572 m

W = 609.90 J

or

W = 610 J

Hence, this is the required solution.

The magnetic circuit below is excited by a 100-turn coil wound over the central leg. The mean length of the central leg is 5.5cm; the mean length of outer paths (including the part of the iron bar at the bottom) is 15.5cm. The relative permeability of the magnetic material is 2000. The cross-sectional area of all legs is A

Answers

Answer:

Hello your question is incomplete attached below is the complete question and solution

answer;

attached below

Explanation:

Given data:

100-turn coil

mean length of central leg = 5.5 cm

mean length of outer paths = 15.5 cm

relative permeability = 2000

cross sectional area ( A ) = 1 cm^2

distance x = 1 cm  

attached below is a detailed solution

ELE Review questions
POSSIBLE POINTS: 3
Match the energy transformation sequence with the device it describes:
A hair dryer plugged into the wall
a
A hand crank generator emergency radio
A battery operated fan
11 CE to ELE
+ ELE to KE
:: KE to ELE
h
1
2
A Review

Answers

Answer:

1. ELE to KE = Electrical energy conversion to kinetic energy.

2. KE to ELE = kinetic energy conversion to electrical energy.

3. CE to ELE = chemical energy conversion to electrical energy.

Explanation:

The Law of Conservation of Energy states that energy cannot be destroyed but can only be transformed or converted from one form to another.

Some examples of energy are chemical energy, electrical energy, kinetic energy, sound energy, potential energy, light energy, etc.

The transformation of energy from one form to another are described below;

1. A hair dryer plugged into the wall: it involves the conversion of electrical energy to kinetic energy. The energy type present in the wall socket is electrical energy which powers the hair dryer to have kinetic energy i.e the energy possessed due to motion of hair dryer.

2. A hand crank generator emergency radio: it illustrates the conversion of kinetic energy to electrical energy. The hand crank generator possess kinetic energy as it is being wounded before it is then converted into electrical energy which powers the radio.

3. A battery operated fan: it illustrates the conversion of chemical energy to electrical energy. The cells present in battery possess chemical energy that is being converted into electrical energy to power the fan.

Use the graph one more time to help you with this question. Changes in both the North and South occurred due to the .

Answers

Answer:

industrial revolution

Explanation:

proof that the kinetic energy of a moving body is half mv square​

Answers

Answer:

1

Explanation:

A force of 350 N is applied to an object that accelerated at a rate of 5 m/sec2. What is the mass of the object

Answers

Answer:

7/ m5sec per minute ckvhxrsuvj

Need help guys please

Answers

Answer:

6.378 * 10^6 m

Explanation:

Radius = 6378 km

Changing in metres

6378 km = 6378000 m

Now in scientific notation

= 6.378 * 10 ^ 6 m

whk is thefounder of pakistan?​

Answers

Answer:

Muhammad Ali Jinnah (Urdu: محمد علی جناح‎; born Mahomedali Jinnahbhai; 25 December 1876 – 11 September 1948) was a barrister, politician and the founder of Pakistan.

Mohammed Ali Jinnah, also called Qaid-i-Azam (Arabic: “Great Leader”), (born December 25, 1876?, Karachi, India [now in Pakistan]—died September 11, 1948, Karachi), Indian Muslim politician, who was the founder and first governor-general (1947–48) of Pakistan

I need help with this, I can't figure it out.
Here is the link:
https://platform.breakoutedu.com/game/play/fun-in-the-sun-140559-XMWCQF1LPL

Answers

Answer:

Star, Triangle, Circle, Rhombus, Square.Left, Down, Right, Down, Up.2,3,2,4.L,O,O,K,I,N,G,F,L,Y.

Explanation: You're welcome ✓

unit 2 Lesson 9: Temperature & Heat Unit Test does anyone have the answers

Answers

Explanation:

where is the question

I did not understood this question

Answers:

Here are the answers for the U2L9: Temperature & Heat Unit Test

1. Which describes how radiation moves?

  B) Radiation moves from a warmer object to a cooler object

2. Which material most likely gets warmer when places in the Sun?

  C) brown mulch

3. A thermogram of a house shows high amounts of thermal energy around the windows but not around the roof. Which conclusion is best supported by the thermogram?

  C) The windows are not energy efficient, but the roof is.

4. Which best describes convection?

  D) It is driven by temperature differences within a fluid.

5. A student heats a liquid on a burner. What happens to the portion of liquid that first begins to warm?

  Any answer you choose is correct on Connexus (look at the screenshot)

6. Convection only occurs in ____.

  B) fluids

7. Conduction involves the transfer of electric charge or ____.

  A) thermal energy

8. A scientist designed a foam container to help keep frozen foods from melting. Which best explains how the foam works?

  D) It reduces the amount of thermal energy that is transferred from the inside to the outside of the container.

9. The diagram shows movement of thermal energy. In which areas of the diagram does conduction occur? (look at the screenshot)

  B) X and Z

10. Nuclear reactions in a reactor produce a lot of thermal energy. That energy then flows and warms up water, which boils and produces steam. The stream then turns turbines that generate electricity. Which statement below can be made about the production of electricity in a nuclear reactor?

  B) Heat flows from the reactor to the water.

11. A stovetop burner on medium reaches 200° C. Which other objects will heat from the burner flow to?

     Any answer you choose is correct on Connexus (look at the screenshot)

12. Heat transfer between two substances is affected by specific heat and the

  D) amount of time and area of physical contact between the substances.

13. Which of these results in kinetic energy of an object?

  B) motion

14. Carmen is heating some water and trying to measure the temperature of water using a Celsius thermometer. Which measurement can she expect once the water begins to boil?

  B) 100° C

15. Which shows the formula for converting from degrees to Celsius to degrees Fahrenheit?

   A) °F = (9/5 × °C) + 32

16. Which of these indicates that a liquid has transferred thermal energy to the air?

  D) The liquid decreases in temperature, and its particles lose kinetic energy.

I took the test ALL of these answers are 100% correct on Connexus (they should be the same for everyone tho)

You're welcome and hope this helps!! :)

6. The temperature at which water molecules have the
LEAST amount of thermal energy is!
a. 0°C b. 32°F c.-273 K d. 0 k

NEEEED THUs now

Answers

The answer is a which is zero

how you use physics in your
everyday life.

Answers

Answer:

Explanation:

Physics gets involved in your daily life right from you wake up in the morning. The buzzing sound of an alarm clock helps you wake up in the morning as per your schedule. The sound is something that you can't see, but hear or experience. Physics studies the origin, propagation, and properties of sound

se the following graph describing a motorcycle's motion to answer the question below.

Answers

I do not see a graph for it?


1When you look through a magnifying glass, the objects you are looking at
seem larger and you can see them in morsetail. The lenses in a magnifying
glass are​

Answers

convex lenses.

eyeglasses with convex lenses increase refraction, and accordingly reduce the focal lenght

You are hiking pine mountain and have finally reached the top. You are peering over the edge and accidentally drop your phone while taking pictures. Your phone falls and hit the
ground 13 seconds later. How tall is the mountain?

Answers

Answer:

The cliff is 12.71m tall.

Explanation:

Why?

Before solving the problem, we must remember that the phone was dropped, it means that there is no initial velocity, also, the acceleration acting on the phone is the acceleration due to gravity.

So, to find how tall is the cliff, we can use the following equations:

\begin{gathered}y=y_o+v_o*t-\frac{1}{2}g*t^{2}\\\\v_f=v_o+g*t\end{gathered}y=yo+vo∗t−21g∗t2vf=vo+g∗t

\begin{gathered}t=\frac{v_f}{g} \\\\t=\frac{-15.75\frac{m}{s}}{-9.81\frac{m}{s^{2}}}=1.61s\end{gathered}t=gvft=−9.81s2m−15.75sm=1.61s

Now that we know the time, we can calculate how tall is the cliff:

\begin{gathered}y=y_o+v_o*t+\frac{1}{2}g*t^{2}\\\\y=0+0*1.61s-\frac{1}{2}*(-9.81\frac{m}{s^{2}})*(1.61s)^{2}\\\\y=12.71m\end{gathered}y=yo+vo∗t+21g∗t2y=0+0∗1.61s−21∗(−9.81s2m)∗(1.61s)2y=12.71m

A positively charged particle of mass 7.2 x 10-8 kg is traveling due east with a speed of 88 m/s and enters a 0.6-T uniform magnetic field. The particle moves through one-quarter of a circle in a time of 2.2 x 10-3 s, at which time it leaves the field heading due south. All during the motion the particle moves perpendicular to the magnetic field. Determine the magnitude of its charge in mC. (1 mC

Answers

Answer:

q = 8.57 10⁻⁵ mC

Explanation:

For this exercise let's use Newton's second law

         F = ma

where force is magnetic force

        F = q v x B

the bold are vectors, if we write the module of this expression we have

         F = qv B sin θ

as the particle moves perpendicular to the field, the angle is θ= 90º

        F = q vB

the acceleration of the particle is centripetal

        a = v² / r

we substitute

        qvB = m v² / r

         qBr = m v

          q =[tex]\frac{m\ v}{B\ r}[/tex]

The exercise indicates the time it takes in the route that is carried out with constant speed, therefore we can use

          v = d / t

the distance is ¼ of the circle,

          d = [tex]\frac{1}{4} \ 2\pi r[/tex]

           d =[tex]\frac{\pi }{2r}[/tex]

we substitute

           v =  [tex]\frac{\pi r}{2t}[/tex]

           r = [tex]\frac{2 \ t \ v}{\pi }[/tex]

           

let's calculate

           r =[tex]\frac{2 \ 2.2 \ 10^{-3} \ 88}{\pi }[/tex] 2 2.2 10-3 88 /πpi

           r = 123.25 m

         

let's substitute the values

           q = [tex]\frac{ 7.2 \ 10^{-8} \ 88}{ 0.6 \ 123.25}[/tex]7.2 10-8 88 / 0.6 123.25

            q = 8.57 10⁻⁸ C

Let's reduce to mC

           q = 8.57 10⁻⁸ C (10³ mC / 1C)

           q = 8.57 10⁻⁵ mC

James makes a treasure map to locate a secret item on McEachern Campus. He uses the
following displacement vectors to locate the treasure
A student wants to simplify this information
5 m East
7 m North
5 m South
7 m East
3 m South
2 m West
A. Determine the Displacement Vector Components. (x componenty component)
Show all work. 2 pts
B. Use the Pythagorean Theorem to calculate the resultant vector. Show all work. 2 pts
Answer format:
a. work & answer...
b. work and answer...
(4 Points)

Answers

Answer:

south

Explanation:

3) What is the weight of an object with a mass of 5.2 kilograms?​

Answers

Answer:

50.96 N

Explanation:

weight = mass x gravity

We know that gravity = 9.8 m/s^2 and mass = 5.2 kg.

w = m x g

w = 5.2 kg x 9.8 m/s^2

w = 50.96 N

The weight of the object is 50.96 N (newtons). Hope this helps, thank you !!

g In principle, both the motion of a simple pendulum and the motion of a mass on a horizontal ideal spring can be used to measure time (via their periods of oscillation). But one of these two types of clocks loses it's accuracy (must be re-calibrated) when taken to high altitudes. Which type of clock is this, and why? Explain in detail please.

Answers

Answer:

In a system with a hanging mass and an inextensible wire, the force is proportional to the sino, in the case of small oscillations, approximately the stop angle, this hiss is lost, the calibration for large amplitudes is lost.

Explanation:

In a spring-mass system the restoring force created by the spring is proportional to displacement from the equilibrium position, therefore this watch does not require streamlining as the amplitude of movement increases.

In a system with a hanging mass and an inextensible wire, the force is proportional to the sino, in the case of small oscillations, approximately the stop angle, this hiss is lost, the calibration for large amplitudes is lost.

A long, thin metal tube of cross-sectional area 1.60 cm2 is sealed into the top of a hollow cube of edge length 0.150 m. Water fills the cube and extends upward a distance h into the tube. Find h if the water exerts a force of 1.00 103 N on the base of the cube. What is the weight of the water?

Answers

Answer:

Explanation:

Given that:

The area of the metal tube = 1.60 cm² = 1.60 × 10⁻⁴ m²

Length of cube L = 0.150 m

The exerted force by water = 1.00 × 10³ N

At the top of the cube;

The force on water is F = pgL

F = 9.8 m/s² × (1000 kg/m³) (0.150 m)(0.150 m)²

F = 33.075 N

[tex]pgh = \dfrac{F}{A}[/tex]

[tex]h = \dfrac{F}{Apg}[/tex]

[tex]h = \dfrac{33.075}{(1.60 \times 10^{-4} \ m^2) \times (1000 \ kg/m^3)(9.8)}[/tex]

h = 21.09 m

The volume of the water V = L³

V = (0.150 m)³

V = 0.003375 m³

weight of the water w = p(V + Ah)

w = 1000 (0.003375 + (1.60 × 10⁻⁴ × 21.09))

w = 6.75 kg

1) A spring, which has a spring constant k=7.50 N/m, has been stretched 0.40 m from ts equilibrium position . What the potential energy now tored in the spring ?

Answers

Answer:

[tex]\displaystyle U_s = 0.6 \ J[/tex]

General Formulas and Concepts:

Math

Pre-Algebra

Order of Operations: BPEMDAS

Brackets Parenthesis Exponents Multiplication Division Addition Subtraction Left to Right

Physics

Energy

Elastic Potential Energy: [tex]\displaystyle U_s = \frac{1}{2} k \triangle x^2[/tex]

U is energy (in J)k is spring constant (in N/m)Δx is displacement from equilibrium (in m)Explanation:

Step 1: Define

k  = 7.50 N/m

Δx = 0.40 m

Step 2: Find Potential Energy

Substitute in variables [Elastic Potential Energy]:                                        [tex]\displaystyle U_s = \frac{1}{2} (7.50 \ N/m) (0.40 \ m)^2[/tex]Evaluate exponents:                                                                                      [tex]\displaystyle U_s = \frac{1}{2} (7.50 \ N/m) (0.16 \ m^2)[/tex]Multiply:                                                                                                           [tex]\displaystyle U_s = (3.75 \ N/m) (0.16 \ m^2)[/tex]Multiply:                                                                                                           [tex]\displaystyle U_s = 0.6 \ J[/tex]

A pendulum Bob released from some initial height such that the speed of the bob at the bottom of the swing is 1.9m/s. What is the initial height of the bob?

Answers

Answer:

h = 18.4 cm

Explanation:

Given that,

The speed of the bob at the bottom of the swing is 1.9m/s.

We need to find the initial height of the bob. Let it is h.

We can find it using the conservation of energy i.e.

[tex]mgh=\dfrac{1}{2}mv^2[/tex]

Where

v is speed of the bob

So,

[tex]h=\dfrac{v^2}{2g}\\\\h=\dfrac{(1.9)^2}{2\times 9.8}\\\\h= 0.184\ m[/tex]

or

h = 18.4 cm

So, the initial height of the bob is 18.4 cm.

The initial height of bob will be "18.4 cm".

Speed and height:

Speed would be the scalar quantity that describes "how quickly an attribute moves." This could sometimes be defined as this same rate whereby an object travels a given distance.

According to the question,

The speed of the bob = 1.9 m/s

Let,

The initial height be "h".

By using the conservation of energy, we get

→ mgh = [tex]\frac{1}{2}[/tex]mv²

or,

→      h = [tex]\frac{v^2}{2g}[/tex]

By substituting the values, we get

          = [tex]\frac{(1.9)^2}{2\times 9.8}[/tex]

          = 0.184 m or,

          = 18.4 cm

Thus the above answer is correct.

Find out more information about speed here:

https://brainly.com/question/13665920

PLZ SOLVE ALL 10
1. What are the six nutrients? Which nutrients provide energy?


2. What percentage of your diet should come from carbohydrates? From protein?


3. What is the primary role of carbohydrates in the body? What are the two major types of carbohydrates?

4. Where does Fiber come from? How much should you consume per day?


5. What is the primary function of protein in the body?


6. What is the primary role of fat in the body?


7. What are the major types of fat? What types of fat are most dangerous to your health?


8. What are vitamins, and why are they important?


9. What are minerals, and why are they important?


10. How much of the human body is made of water? How much fluid should an average person drink each day?

Answers

1) Carbohydrates, Lipids (fats), Protein, Vitamins, Minerals, and Water. proteins, fats and carbs provide energy.

2) 45 to 65 percent carbs, and 10-35 percent protein.

3) Carbs are your body's main source of energy. the 2 major types are simple and complex carbs

4) cereals, fruits and vegetables. You should have 25 to 30 grams a day.

5) It helps repair and build your body's tissues, allows metabolic reactions to take place and coordinates bodily functions.

6) It gives you energy and supports cell growth.

7) Saturated fats, Trans fats, Monounsaturated fats, and Polyunsaturated fats. trans fats are the most dangerous for your health

8) Vitamins and minerals are considered essential nutrients, They help shore up bones, heal wounds, and bolster your immune system. They can also help convert food into energy.

9) Minerals help build strong bones to transmitting nerve impulses. Some minerals are even used to make hormones or maintain a normal heartbeat.

10) 60% is made of water, 11 to 15 cups of water should be drank a day.

hope this helps :)

Which list below contains only ionic compounds?
A. CaCl2, H2O, LIF
B. CO2, K20, P4010
C. LiF, CaCl2, Mgo
D. NO2, Mgo, CuCl2

Answers

Answer:

C. LiF, CaCl2, MgO

Explanation:

Ionic compound: It is that compound which consist of negative and position ions and held together by electrostatic force of attraction.

The ionic compound is neutral.

The ionic compound formed between metal and non-metal.

Covalent compound: It is that compound in which sharing of electrons between two atoms occur.

A.[tex]CaCl_2,H_2O,LiF[/tex]

H2O is not ionic compound. It is polar covalent.

Therefore, it does not contain only ionic compounds.

B.CO2,K2O,P4O10

CO2 and P4O10 are not ionic .It is covalent.

Therefore, it does not contain only ionic compounds.

C. LiF,CaCl2 ,MgO

All compounds are ionic because in given compounds one ion is negative  and one is metal (positive).

Therefore, it contains only ionic compounds.

D.NO2,MgO,CuCl2

NO2 is not ionic.

Therefore, it does not contain only ionic compounds.

Option C is correct.

Other Questions
How did the Jews create and maintain their own distinct cultural identity? What features do all right trlangles have in common? (GIVING BRAINLIEST!!!)0.5 g of salt is equal to how many milligrams? Show all of your calculations. What role do you think an independent judiciary, separate from the legislative and executivebranches, plays in a constitutional democracy? CAN SOMEONE HELP ME PLZ I NEED HELP describe a time when you showed self discipline HELPPPP PLEASE ANSWER THIS CORRECTLY AND U WILL GET BRAINLIEST WHAT IS THE SOLUTION TO THIS PROBLEM There is 1 teacher for every 18 students on a school trip. How many teachers are there if 72 students go on the school trip?Move values to create a proportion that can be used to solve the problem. Complete the following sentence. Even if someone does not get the job after an interview, she or he should be sure to ____ the person who interviewed her or him. [tex]\frac{\sqrt[3]{60} }{\sqrt[3]{36} }[/tex] Decide if the following sentence is grammatically correct or incorrect.Paul est entre Suzanne et Martine.O CorrectO Incorrect An initially motionless test car is accelerated to 115 km/h in 8.58 s before striking a simulated deer. The car is in contact with the faux fawn for 0.815 s, after which the car is measured to be traveling at 60.0 km/h. What is the magnitude of the acceleration of the care before the collision? What is the magnitude of the average acceleration of the car during the collision? Pick out the solution from the values given in the bracket next to each equation. Show that the other values do not satisfy the equation. a. X + 12 = 20 ( 12,8,20,0) b. P - 4 = 0 (4,-4,8,0) c. 2y - 3 = 7 (0,3,5,7) Plz explain ;) Do not go gentle into that good night,Old age should burn and rave at close of day;Rage, rage against the dying of the light.Though wise men at their end know dark is right,Because their words had forked no lightning theyDo not go gentle into that good night.Which statement best expresses the theme of thepoem?Death is inevitable, so there is no point in trying toresist itThe cruelty of death is that we do not know whenit will happenNo matter what, it is important to struggle to stayalive. What was the law called which forced American Indians to move? Abby is writing a biography of Isaac Newton. He was a brilliant English scientist who developed the law of universal gravitation in the 1600s. Newton also developed laws of motion and ideas about inertia. His laws and ideas were used in many subjects such as physics, astronomy, and mathematics. Explain inertia using Newton's first law of motion. Give an example of inertia. T puedes aprender ms if you try harder.You can teach betterYou can learn moreYou can study fasterYou can read more What is the perimeter of the triangle?Please help ASAP! Which of the following electronic transitions in the oxygen atom will result in light emission?A.n i= 1nf = 2B.n i= 1nf =3 C. n i =3n f =2 D. n i =2n f =3 Help me please and thank you