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JAMB Physics Past Questions & Answers - Page 20

96.

A magnet relay is a device used for?

A.

reading the magnitude of magnetic flux

B.

controlling another circuit carrying larger current

C.

turning in sports

D.

storing magnetic field

Correct answer is B

Relays are electrically operated switches that open and close the circuits by receiving electrical signals from outside sources.

97.

When the plate area of a capacitor increases?

A.

the voltage can withstand increase

B.

the capacitance decreases

C.

the capacitance is unaffected

D.

the capacitance increases

Correct answer is D

Therefore, as the area of the plates increase, capacitance increases.

98.

A tuning fork having a frequency of 312 Hz emits a wave which has a wavelength of 1.10 m. Calculate the velocity of sound

A.

312.0 ms1

B.

110.0 ms1

C.

343.2 ms1

D.

686.4 ms1

Correct answer is C

v = f λ to calculate the wave's velocity.

v = 312 x 1.10

= 343.2m/s

99.

A person standing waist-deep in a swimming pool appears to have short legs because of light?

A.

diffraction

B.

refraction

C.

reflection

D.

interference

Correct answer is B

The refractive index of water is greater than that of air.

So, A person legs appear to be short while standing in the tank due to refraction.

100.

The secondary pigments consist of?

A.

blue, green, and violet

B.

yellow, green, and magenta

C.

magenta, yellow, and cyan

D.

red, green, and blue

Correct answer is C

The primary colors of pigment are red, blue, and green.

Mixing these primary colors of pigment gives us the three secondary colors: 

red+blue=magenta, red+ green = yellow, and blue + green = cyan