Electromagnetic Induction - Jamb Physics Past Questions and Answers

Question 26:

• 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 27:

• 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 28:

• 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