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

Question 21:

• JAMB 2006

The main purpose of the transformer in an a.c radio set is to?

A. Increase power to the radio
B. Step up the voltage
C. Convert energy from a.c to d.c
D. Step down the voltage

Question 22:

• JAMB 2007

Lenz's law is a law of conservation of

A. Electric charge
B. Electric current
C. Energy
D. Momentum

Question 23:

• JAMB 2008

The d.c generator has essentially the same components as the a.c generator except the presence of?

A. Slip-ring
B. Carbon brushes
C. Split ring
D. Armature

Question 24:

• JAMB 2008

A step-down transformer has a power output of 50 W and efficiency of 80%. if the mains supply voltage is 200 v, calculate the primary current of the transformer.

A. 0.31 A
B. 3.20 A
C. 3.40 A
D. 5.00 A

Question 25:

• JAMB 2012

The core of an efficient transformer should consist of laminated pieces of metal in order to

A. Increase the heat produced by increasing the eddy current
B. Increase the heat produced by reducing the eddy current
C. Reduce the heat produced by increasing the eddy current
D. Reduce the heat produced by reducing the eddy current