Jamb Physics 1981 Past Questions and Answers

Question 41:

• 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 42:

• 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 43:

• 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

Question 44:

• JAMB 1981

A solid weighs 4.8g in air, 2.8g in water and 3.2g in kerosine. The ratio of density of the solid to that of the kerosine is

A. 12
B. 3
C. 2
D. \(\frac{3}{2}\)
E. \(\frac{5}{4}\)

Question 45:

• JAMB 1981

A body of mass 6kg rests on an inclined plane. The normal reaction is R and the limiting frictional force is F as shown in the image above. if F = 30N, and g = 10ms² then the angle of inclination \( \theta \) is

A. \( 15^{\circ} \)
B. \( 30^{\circ} \)
C. \( 45^{\circ} \)
D. \( 60^{\circ} \)
E. \( 75^{\circ} \)