WAEC Physics Past Questions & Answers - Page 296

1,476.

How long will it take to heat 3 kg of water from 28^oC to 88^oC in an electric taking a current of 6 A from an e.m.f. source of 220V?

A.

96s

B.

1.20s

C.

570s

D.

600s

E.

1200s

View answer & explanation

Correct answer is C

Ivt = mcΔθ

t =

mcΔθ/Iv

=

3x 4200 x (88 - 28)/6 x 200

1,477.

A rectangular coil of wire can rotate in a magnetic field. The ends of the coil are soldered to the two halves of a split ring. Two carbon brushes are made to press lightly against the split ring and when these are connected in circuit with a battery and rheostat, the coil rotates. This is a description of

A.

a suspended- coil vanometer

B.

a moving-cell ammeter

C.

a d.c generator

D.

an electric motor

E.

an induction coil,

View answer & explanation

Correct answer is C

No explanation has been provided for this answer.

1,478.

A cell of e.m.f. 1.5 V and internal resistance of 2.59 is connected in series with an ammeter of resistance 0.59 and a resistor of resistance 7.09. Calculate the current in the circuit.

A.

0.15 A

B.

0.20 A

C.

0.60A

D.

3.00A

E.

6.67 A

View answer & explanation

Correct answer is A

No explanation has been provided for this answer.

1,479.

Birds can perch safely on overhead electric power cables without being electrocuted because

A.

birds can withstand high p.d. of the electric power cables

B.

any accumulated charge on the birds is quickly dissipated

C.

the feet of the birds are well insulated

D.

the current is a.c. and has particular direction

E.

there is no p.d between the birds and the cables

View answer & explanation

Correct answer is C

No explanation has been provided for this answer.

1,480.

Calculate the resistance of the filament of a lamp rates 240 V, 40 W

A.

240Ω

B.

360Ω

C.

720Ω

D.

1440Ω

E.

2880Ω

View answer & explanation

Correct answer is D

R = V²/P = 240²/40 = 1440Ω

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