JAMB Physics Past Questions & Answers - Page 408

2,036.

Two charged particles are projected into a region where there is a magnetic field perpendicular to their velocities. if the charges are deflected in opposite directions, which of the following statements is true of the charge?

A.

the charge must be of opposite sign

B.

positive charges are more in number

C.

the charges are electrically neutral

D.

the charges are of the same sign

Correct answer is A

The charge must be opposite in sign, since the positive charges will deflect to the negative plate, and the negative charge to the positive plate

2,037.

The electric field intensity in a place where a charge of 10-10c experiences a force of 0.4N is?

A.

4.0 x 107 NC-1

B.

8.0 x 109 NC-1

C.

8.O x 10-12 NC-1

D.

4.0 x 109 NC-1

Correct answer is D

The electric force experienced in an electric field of intensity E is given by:
F = qE: where q = the test charge.
E = F/Q = 0.4/10-10 = 0.4 X 10-10
= 4.0 X 109 NC-1

2,038.

A car battery rated 45 A H is charged with a charger whose rating is 2.5A.How long will it take to charge the battery full?

A.

10 hrs

B.

18 hrs

C.

20 hrs

D.

25 hrs

Correct answer is B

For a car battery rated 45 AH, being charged by a charger of 2.5 A rating, the time for the battery to be fully charged is given by:
T = (45)/2.5 = 18 hrs

2,039.

The north pole of a magnet can never be separated from the south pole because of the property knowledge as?

A.

magnetic octopole

B.

magnetic monopole

C.

magnetic dipole

D.

magnetic quadrupole

Correct answer is C

No explanation has been provided for this answer.

2,040.

An electric device is rated 2000 W, 250 v. The correct fuse rating of the device is?

A.

9 A

B.

8 A

C.

6 A

D.

7 A

Correct answer is B

For the device rated 2000 W, 250 V, implies that current I, flowing is given by the relation
Power = IV
I = (power)/v = (200)/250
= 8A.
∴ the most suitable fuse for the device is 8A