Question 191:

• JAMB 1981

Which of the following is NOT directly associated with direct current (DC)?

A. A dry cell
B. A moving coil galvanometer
C. A transformer
D. A lead- acid accumulator
E. A commutator

Question 192:

• JAMB 1981

The relationship between the period T and the length T of a smile pendulum is T = 2\( \pi \) \( ( \frac{I}{g}) ^{ \frac{1}{2} } \). From experiment data of T and I, one can obtain the following graphs, i. T vs.I ii. T vs I² iii. T² vs. I iv. T vs \( \sqrt{I} \) v. logT vs logI. Which of the following graphs, are linear?

A. All
B. Only i and ii
C. Only iii and iv
D. Iii,iv and v
E. None of them

Question 193:

• JAMB 1981

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
E. 25 volts

Question 194:

• JAMB 1981

A closed coil of wire is placed near a magnet. The magnet lies along the axis of the coil. Under which of the following conditions would there be no current in the coil?

A. When the coil is moved toward the stationary magnet
B. When the coil is moved away from the stationary magnet
C. When the coil is held stationary but the magnet is moved towards the coil
D. When both the coil and the magnet are held stationary
E. When the coil is held stationary but the magnet is moved away from the cell

Question 195:

• JAMB 1981

If I is the current passing through a metallic resistor and H is the rate of Heat generated in the resistor at a constant temperature, then

A. H \(\alpha\) \(\frac{1}{I}\)
B. H \(\alpha\) \(\frac{1}{I^2}\)
C. H \(\alpha\) \(\sqrt1\)
D. H \(\alpha\) I²
E. None of the above