Question 611:

• JAMB 1990

What precaution should a manufacturer take to ensure that energy loss in a transformer is minimized?

A. The winding of the transformer should be made of high resistance wire
B. The core should be made of thin sheets of metal
C. No magnetic material should be used to make the core
D. The flux linking the primary with the secondary coils should be minimum

Question 612:

• JAMB 1990

A substance has a half of 3mins. after 6mins. the count rate was observed to be 400. What was its count rate at zero time?

A. 200
B. 1200
C. 1600
D. 2400

Question 613:

• JAMB 1990

The photocell works on the principle of the

A. Voltaic cell
B. Emision of electrons by incident radiation
C. Emision of protons by incident electrons
D. Photographic plate

Question 614:

• JAMB 1990

What is the reading of the vernier scale above

A. 1.88cm
B. 1.80cm
C. 1.28cm
D. 1.97cm

Question 615:

• JAMB 1990

Two horizontal forces, 10N and 8N and another force F1 inclined at 30 to the vertical acting as shown in the diagram above, keep the body P in equilibrium, The weight of the body is

A. 2√3/3N
B. √2N
C. 4√3/3
D. 2V3N