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2021 - JAMB Physics Past Questions and Answers - page 4

31

The temperature gradient across a copper rod of thickness 0.02m, maintained at two temperature junctions of 20º and 80ºC respectively is?

A

3.0 x 10\(^{2}\)km\(^{-1}\)

B

3.0 x 10\(^{3}\)km\(^{-1}\)

C

5.0 x 10\(^{3}\)km\(^{-1}\)

D

3.0 x 10\(^{4}\)km\(^{-1}\)

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32

Calculate the mass of ice that would melt when 2kg of copper is quickly transferred from boiling water to a block of ice without heat loss (specific heat capacity of copper = 400Jkg\(^{1}\)k\(^{-1}\), latent heat of fusion of ice = 3.3 x 10\(^{5}\)Jkg\(^{-1}\))

A

\(\frac{8}{33}\)kg

B

\(\frac{3.3}{80}\)kg

C

\(\frac{80}{33}\)kg

D

\(\frac{3.3}{8}\)kg

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33

The equation of a wave traveling along the positive x-direction is given by; y = 0.25 x 10\(^{-3}\) sin (500t - 0.025x). Determine the angular velocity of the wave motion. 

A

0.25 x 10\(^{-3}\)rads\(^{-1}\)

B

0.25 x 10\(^{-1}\)rads\(^{-1}\)

C

5.00 x 10\(^{2}\)rads\(^{-1}\)

D

2.50 x 10\(^{3}\)rads\(^{-1}\)

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34

If a sound wave goes from a cold air region to a hot air region, its wavelength will...?

A

increase

B

decrease

C

decrease then increase

D

remain constant

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35

The lowest note emitted by a stretched string has a frequency of 40Hz. How many overtones are there between 40Hz and 180Hz?

A

4

B

3

C

2

D

1

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36

A man stands 4m in front of a plane mirror. If the mirror is moved 1m towards the man, the distance between him and his new image is?

A

3m

B

5m

C

6m

D

10m

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37

The inside portion of part of a hollow metal sphere of diameter 20cm is polished. The portion will therefore form a?

A

concave mirror of focal length 5cm

B

concave mirror of focal length 10cm

C

convex mirror of focal length 5cm

D

convex mirror of focal length 10cm

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38

The velocities of light in air and glass are 3.0 x 10\(^8\)ms\(^{-1}\) and 2.0 x 10\(^8\)ms\(^{-1}\) respectively. If the angle of refraction is 30º, the sine of the angle of incidence is? 

A

0.33

B

0.50

C

0.67

D

0.75

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39

An astronomical telescope is said to be in normal adjustment when the?

A
eye is accommodated
B
focal length of an object lens is longer than that of eye piece
C
final image is at the near point of eye
D
final image is at infinity
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40

A 2H inductor has negligible resistance and is connected to a \(\frac{50}{\pi}\) Hz A.C supply. The reactance of the inductor is?

A
200\(\Omega\)
B
50\(\Omega\)
C
\(\frac{100}{\pi}\)
D
\(\frac{25}{\pi \Omega}\)
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