JAMB Physics Past Questions & Answers - Page 97

481.

The angle which the direction of the earth magnetic field makes with the horizontal at a palace is know as.

A.

angle of contact

B.

angle of dip

C.

angle of declination

D.

magnetic meridian

Correct answer is B

No explanation has been provided for this answer.

482.

The mass of the earth is 6.0 x 1024kg and that of the moon is 7.0 x 1022kg. If the distance between them is 4.0 x 108m, calculate the force of attraction between them. [G = 6.7 x 10-11Nm2kg-2]

A.

1.8 x 105N

B.

1.8 x 1010N

C.

1.8 x 1015N

D.

1.8 x 1020N

Correct answer is D

F = \(\frac{GM_1M_2}{12^2}\)

F = 6.7 x 10-11x

F = \(\frac{M_1M_2}{R^2}\)

F = \(\frac{6.7 \times 10^{-11} \times 6.0 \times 10^{24} \times 7.0 \times 10^{22}}{(4 \times 10^8)^2}\)

= 1.8 x 1020N

484.

A wire of cross-sectional area 0.60mm2 has a restivity of 7.2 x 10-7 \(\Omega\). Calculate the length of wire that will have a resistance of 3\(\Omega\).

A.

0.25m

B.

2.50m

C.

3.60m

D.

36.00

Correct answer is B

R = \(\frac{PL}{A}\)

C = \(\frac{RA}{P}\)

C = \(\frac{0.60 \times 10^{-6} \times 3}{7.2 \times 10^{-7}}\)

C = 2.50m

485.

The symbol illustrated above is that of a resistor?

A.

which absorb light

B.

which emits light

C.

which absorbs heat to function properly

D.

whose resistance is light dependent

Correct answer is D

A photoresistor or light dependent resistor is an electronic component that is sensitive to light. When light falls upon it, then the resistance changes.

Used where there is a need to sense the presence and absence of light is necessary. These resistors are used as light sensors and the applications of LDR mainly include alarm clocks, street lights, light intensity meters, burglar alarm circuits.