WAEC Physics Past Questions & Answers - Page 285

1,421.

The diagrams above show lines of force in electric fields. In which of the diagrams would a positive test charge experience the least force as it moves from x to y?

A.

I only

B.

II only

C.

III only

D.

I and II only

E.

II and III only

Correct answer is A

No explanation has been provided for this answer.

1,422.

Calculate the energy stored in 20μF capacitor if the potential difference between the plates is 40 V.

A.

3.2 x10-2J

B.

1.6x102J

C.

8.0x10-4J

D.

4.0x10-4J

E.

2.0x10-4J

Correct answer is B

E = 1/2cv2 = 1/2 x 10 x 10-6 x 402 = 1.6 x 10-2J

1,423.

Which of the following statements is not correct?

A.

A magnetic Held is a region where a magnetic force can be detected.

B.

Magnetic fields are scalar quantities.

C.

The magnitude of the magnetic force experienced by a moving charge depends on the speed on the charge.

D.

the angle between the direction of the earth’s magnetic held and the horizontal is called the angle of dip.

E.

Iron filings can be used to trace out the magnetic field around a bar magnet.

Correct answer is B

No explanation has been provided for this answer.

1,424.

Lenz’s law of electromagnetic induction states that

A.

electromotive force is induced in a circuit whenever there is a change in the magnetic flux linked with the circuit

B.

the induced current in a conductor is in such a direction as to oppose the change producing it

C.

the induced e.m.f. in a circuit is proportional to the rate of change of number of lines of force linking the circuit

D.

a force is exerted on a current carrying conductor in a magnetic field

E.

the induced e.m.f. is proportional to the current producing the magnetic flux.

Correct answer is B

No explanation has been provided for this answer.