(a) Electromagnetic Induction - Jamb Physics Past Questions and Answers

Question 31:

• JAMB 2015

The strength of an electromagnet increase with

A. Increase in the number of turn of the coil
B. Decrease in current with the coil
C. Increase in the distance between the pole
D. Increase in current without the coil

Question 32:

• JAMB 2015

Transformers are designed so that energy losses are reduced to a minimum. This is achieved through those process.
I. Using a soft iron ore
II. Laminating the iron core to reduce energy loses due to eddy current
III. Designing an efficient iron core

A. I & II only
B. II only
C. I, II, & III only
D. III only

Question 33:

• JAMB 2015

Efficiency of a transformer is equal to

A. Efficiency of transformer = (secondary coil à· primary coil) à— 100%
B. Efficiency of transformer = (mechanical advantage ÷ velocity ratio) × 100%
C. Efficiency of a transformer = (Number of turns in the secondary coil à· Number of turns in the primary coil) à— 100%
D. Efficiency of a transformer = (power developed in the secondary coil à· power supplied to the primary coil) à— 100%

Question 34:

• JAMB 2017

How can energy loss be minimized through Eddy-current?

A. By using high resistance wire
B. By using insulated soft iron wires
C. By using low resistance wires
D. Bu using turns of wires

Question 35:

• JAMB 2020

A transformer has 300 turns of wire in the primary coil and 30 turns in the secondary coil. If the input voltage is 100 volts, the output voltage is

A. 5 volts
B. 10 volts
C. 15 volts
D. 20 volts