1994 - JAMB Physics Past Questions & Answers - page 4

31
Which of the following has the lowest internal resistance when new?
A
leclanche cell
B
Daniel cell
C
Accumulator
D
Torch battery
CORRECT OPTION: c
32
When a biro pen rubbed on a dry silk cloth is moved very close to a piece of paper on a dry table, the pen is found to pick up the paper. This is because
A
both the pen and the cloth are magnetized
B
the pen is magnetized but the cloth is not
C
the pen is charged while the cloth is magnetized
D
both the pen and the cloth are charged
CORRECT OPTION: d
They are all charged either positively or negatively
33
A capacitor 8\(\mu\)F is charged to a potential difference of 100V. The energy stored by the capacitor is
A
1.0 x 104J
B
8.0 x 10J
C
1.25 x 10J
D
4.0 x 10-2J
CORRECT OPTION: d
Energy = \(\frac{1}{2}\)CV2

= \(\frac{1}{2}\) x 8 x 10-6 x (100)2

= 4 x 10-2J
34
Two capacitors R1 = 4\(\Omega\) and R2 = 5\(\Omega\) are connected in parallel across a potential difference. If P1 and P2 represent power dissipated in R 1 and R2 respectively, then the ratio P1 : P2 is
A
4 : 5
B
5 : 4
C
16 : 25
D
25 : 16
CORRECT OPTION: b
P1 = \(\frac{V^2_1}{R_1}\) and P2 = \(\frac{V^2_2}{R_2}\)

P1R1 = P2R2

4P1 = 5P2

\(\frac{p_1}{p_2}\) = \(\frac{5}{4}\)

= 5 : 4
35
Which of the following are found in the receiver but not in the microphone of a telephone handset? i. Diaphragm. ii. soft iron pole pieces. iii. permanent magnet. iv.carbon blocks
A
i and ii
B
i and iv
C
ii and iii
D
iii and iv
CORRECT OPTION: b
36
If two parallel conductors carry currents flowing in the same direction, the conducts will
A
attract each other
B
repel each other
C
both move in the same direction
D
have no effect on each other
CORRECT OPTION: a
37
A certain radioisotope of \(^{235}_{92}U\) emits four alpha particles and three beta particles. The mass number and the atomic number of the resulting elements respectively are
A
219 and 87
B
84 and 223
C
223 and 87
D
219 and 81
CORRECT OPTION: a
\(^{235}_{92}U\) \(\to\) 4\((^{4}_{2}\alpha)\) + 3\((^{0}_{-1}e)\) + \(^{b}_{a}y\)

a + (4 + 2) + (3x - 1) = 92 \(\Rightarrow\) a = 87

b + (4 x 4) + (3 x 0) = 235 \(\Rightarrow\) b = 219

\(^{b}_{a}Y\) = \(^{219}_{87}Y\)
38
If light with photon energy 2eV is incident suitably on the surface of a metal with work function 3eV, then
A
no electron will be emitted
B
the few electrons emitted will have a maximum kinetic energy of 1eV
C
the few electrons emitted will have a maximum kinetic energy of 3eV
D
many electrons will be emitted
CORRECT OPTION: a
An electron can only be emitted if photon energy is equal or greater than work function of the plate
39
A spring of length 25cm is extended to 30cm by a load of 150N attached to one of its end, what is the energy stored in the spring?
A
3750J
B
2500J
C
3.75J
D
2.50J
CORRECT OPTION: c
40
What is the reading of the vernier calipers shown above
A
1.79cm
B
1.73cm
C
1.39cm
D
1.34cm
CORRECT OPTION: c
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