WAEC Past Questions and Answers - Page 2838

14,186.

A body of mass, M, moving with velocity, V, has a wavelength, X, associated with it. This phenomenon is called----------

A.

photoelectric effect

B.

heisenberg's uncertainty principle

C.

compton effect

D.

wave-particles paradox

Correct answer is A

The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material

14,187.

The magnetic material produced from the chemical combination of metal oxides and has a very high resistance to electric current is called

A.

ferrite substance

B.

paramagnetic substance

C.

ferromagnetic substance

D.

diamagnetic substance

Correct answer is A

Ferrite magnets are non-conductive aferromagnetic ceramic compounds derived from iron oxides such as Haematite (Fe203) or Magnetite (Fe304) and other metal oxides such as Barium and Strontium.

Ferrite is a polycrystal, sintered material with high electrical resistivity. The high resistance of ferrite makes eddy current losses extremely low at high frequencies.

14,188.

The period of a 10 kHz radio wave traveling at 10\(^{8}\) ms\(^{-1}\) is--

A.

3.0 x 10\(^{-5}\)s

B.

1.0 x 10\(^{-4}\) s

C.

1.0 x 10\(^{4}\)s

D.

3.0 x 10\(^{4}\)s

Correct answer is B

The relation between period and frequency is that one is the inverse of the other.

By definition:

Frequency = 1/period.

or 

period = 1/frequency → 1/ 10,000

period = 0.0001 or 1.0 x 10\(^{-4}\) s

 

14,189.

Current is passed through two parallel conductors in the same direction. If the conductors are placed near each other, they will------------------

A.

move in a circle

B.

repel each other

C.

remain stationary

D.

attract each other

Correct answer is D

Two conductors with current flowing in the same direction will attract. 

14,190.

The reason for having a large number of turns in the coil of a moving coil galvanometer is to--------

A.

make the deflection of the needle proportional to the current

B.

increase the sensitivity of the galvanometer

C.

decrease the magnetic flux produced by the magnet

D.

make the permanent magnet stronger

Correct answer is B

Sensitivity of a galvanometer increases when number of turns, area of coil and magnetic field increase