**Electromagnetic Induction Questions and Answers with Discussion – Electromagnetic Induction ***(Electromagnetic induction)* An electric current is caused by a change in magnetic flux. Magnetic flux is the number of magnetic lines of force that pass through a plane. A scientist from Germany named Michael Faraday had the idea that magnetic fields can produce electric currents.

Electromagnetic induction is a symptom of the emergence of an electromotive force in a coil/conductor when there is a change in the magnetic flux in the conductor or when the conductor moves relatively across a magnetic field.

## 1 – 10 Electromagnetic Induction Questions and Answers and Discussion

1. A 50 cm long wire PQ is driven perpendicularly along wire AB cutting a uniform magnetic field of 0.02 Tesla as shown in the figure.

Define:

a) large induced emf

b) the current flowing in the wire PQ

c) the direction of the current in the wire PQ kawat

d) higher potential between points P and Q

e) the magnitude of the Lorentz force on PQ

f) the direction of the Lorentz force on PQ

g) power absorbed resistance R = 0.02

**Discussion**

a) large induced emf

Note: The sign (−) in the formula is omitted to simplify calculations, the resulting absolute value remains the same.

b) the current flowing in the wire PQ

c) the direction of the current in the wire PQ kawat

The right hand rule for the direction of the induced current:

- 4 fingers = magnetic field direction (B)
- thumb = direction of motion of the wire (v)
- palm = direction of induced current (i)

Current direction from P to Q (or from Q to P through resistance R)

d) higher potential between points P and Q

The potential P is higher than Q because the current flows from the higher potential to the lower potential.

e) the magnitude of the Lorentz force on PQ

f) the direction of the Lorentz force on PQ

The right hand rule for determining the direction of the Lorentz force (magnetic force):

– 4 fingers = direction of magnetic field strength (B)

– thumb = direction of electric current (i)

– palm = direction of force (F)

The direction of the force F is to the left (opposite to the direction of motion v)

g) power absorbed resistance R = 0.02

2. A coil with 1000 turns undergoes a change in magnetic flux of 3 x 10^{5}Wb becomes 5 x 10^{5}Wb in an interval of 10 ms. Determine the resulting induced emf!

**Discussion**

Data from questions:

Number of turns N = 1000

Time interval t = 10 ms = 10 x 10^{3} second

Flux difference = 5 x 10^{5}3 x 10^{5} = 2 x 10^{5} Wb

3. A coil with 10 turns undergoes a change in magnetic flux by the equation:

= 0.02 t^{3}+0.4 t^{2}+ 5

with in Weber units and t in seconds. Determine the magnitude of the induced emf when t = 1 second!

4. An AC generator produces a voltage according to the following equation:

5. A coil with an inductance of 5 mH experiences a change in the current flowing from 0.2 A to 1.0 A in 0.01 second. Determine the magnitude of the stress that arises as a result of this event!

**Discussion**

Data from questions:

Coil inductance L = 5 mH = 5 x 10^{3} H

Current change i = 1.0 0.2 = 0.8 A

Time interval t = 0.01 second se

6. The emf at the ends of the coil occurs if the coil . . . .

A. There is a strong magnetic field

B. there are a fixed number of magnetic lines of force

C. is in the vicinity of a strong magnetic field

D. there is a change in the number of magnetic lines of force

**Answer: A**

#### Also read: Example of Lorentz Transformation Questions and Answers [+Pembahasan]

7. Pay attention to the table about transformers:

Which includes the type of step up transformer is …

A. 1 and 2

B. 1 and 3

C. 2 and 4

D. 3 and 4

**Discussion: **

Step up transformer = voltage step up

Vp / Vs = Np / Ns = is / ip

If Vp < Vs, then

From the table that fulfills are (3) and (4)

8. If the bicycle dynamo spins faster, then the bicycle light turns on…

A. bright because the magnetic field on the dynamo is getting stronger, so the current in the lamp is getting bigger

B. bright because the change in the magnetic field of the dynamo is getting faster, so the emf is getting bigger

C. dim because the coil is difficult to cut the magnetic lines of force, so the emf is getting smaller

D. bright, because the change in the magnetic field on the dynamo is getting faster, so the resistance of the dynamo is getting smaller

**Answer: A**

9. The magnetic flux enclosed by a coil decreases from 0.5 Wb to 0.1 Wb in 5 seconds. The coil consists of 200 turns with a resistance of 4 . How strong is the electric current flowing through the coil?

**Solution:**

**Is known:**

Φ_{1} = 0.5 Wb

Φ_{2} = 0.1 Wb

N = 200 turns

R = 4Ω

t = 5 seconds

Asked: I… ?

Discussion:

The induced emf is calculated by the equation:

the sign (-) indicates the reaction to flux changes, ie the induced flux is in the opposite direction to the main magnetic flux. The current flowing through the coil is:

I = /R = 16/4 = 4 A

10. A wire 2 m long moves perpendicular to a magnetic field with a speed of 12 m/s, at the ends of the wire a potential difference of 1.8 V arises. Determine the magnitude of the magnetic induction!

**Solution:**

Is known: *l* = 2 m; v = 12 m/s; = 1.8 volts

Asked: B = … ?

**Discussion:**

Since V B, the magnitude of the magnetic induction is:

= B.*l*.v

1.8 = B × 2 × 12

1.8 = 24 B

B = 1.8/24 = 0.075 T

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