JAMB Physics Past Questions & Answers - Page 204

1,016.

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

Correct answer is D

H \(\alpha\) I2RT

1,017.

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

Correct answer is D

No explanation has been provided for this answer.

1,018.

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

Correct answer is B

for transformer,

Es = Ns, Es = e.m.f of secondary

Ep = Np, Ep = e.m.f of primary

NS = number of turns in secondary

Ns = number of turns in primary

\(\frac{30}{300}\) = \(\frac{x}{100}\)

300X = 3000X

= 10 volts

1,020.

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

Correct answer is C

No explanation has been provided for this answer.