2020 - JAMB Physics Past Questions and Answers - page 4
Heat is supplied uniformly at the rate of 100W to 1.0 x 10\(^{-2}\)kg of a liquid for 20 seconds. If the temperature of the liquid rises by 5\(^o\)C, then the specific heat capacity of the liquid is
2.0 x 10\(^2\)Jkg\(^-1\)K\(^-1\)
2.0 x 10\(^2\)Jkg\(^-1\)
4.0 x 10\(^4\)Jkg\(^-1\)K\(^-1\)
4.0 x 10\(^4\)Jkg\(^-1\)
Heat energy = Electrical Energy
Hence,
MC\(\theta\) = power x time
5 x 1 x 10\(^{-2}\) x C = 100 x 20
C = \(\frac{200}{5 \times 10^2}\)
= 4 x 10\(^4\) J/kg/\(^oC\)
Two drivers G and H are at depths 20m and 40m, respectively below the water surface in a lake. The pressure on G is O\(_1\) while the pressure on H is P\(_2\), If the atmospheric pressure is equivalent to 10m\(^2\) of water, then the value of P\(_2\)/P\(_1\) is
0.50
0.60
1.67
2.00
Pressure at H = 40m
Pressure at G, P\(_1\) = 20m
\(\frac{P_2}{P_1} = \frac{40}{20}\)
= 2
The fiqure above represents a block-and-tackle pulley system on which an effort of W Newtons supports a load of 120.0N. If the efficiency of the machine is 40\(^o\), then the value of W is
28.0N
48.0N
288.0N
50.0N
V.E = 6, load = 120N
Efficiency = M.A x \(\frac{1}{V.R}\) x 100%
40 = \(\frac{120}{effort}\) x \(\frac{1}{6}\) x \(\frac{100}{1}\)
Effort = 50N
In an experiment in which molten naphtha-line is allowed to cool, the cooling curve i n the figure was obtained. The temperature 80\(^o\)C is known as the
cooling temperature
boiling point
melting point
vaporization point
In the figure, the value of R is
3\(\Omega\)
6\(\Omega\)
4\(\Omega\)
5\(\Omega\)
R\(_T\) = \(\frac{V}{1} = \frac{12}{2}\) = 6\(\Omega\)
R\(_T\) = 3 + \(\frac{R \times 6}{R + 6}\)
R = 6\(\Omega\)
Which of the following instruments consumes the highest current?
|
I. Electric iron II. Television set III. Torch light IV. Immersion heater |
250v 220v 6v 110v |
1kW 110W 30W 500W |
2
I
II
III
IV
(I) I = \(\frac{P}{V} = \frac{1000}{25}\) = 4A
(II) I = \(\frac{110}{220}\) = 0.5A
(III) I = \(\frac{30}{6}\) = 5A
(IV) I = \(\frac{500}{110}\) = 4.55A
Which of the following pairs is NOT part of the electromagnetic spectrum?
I. Radio waves
II. Beta rays
III. Gamma rays
IV. Alpha rays
I and II
III and IV
I and III
II and IV
A substance has half of 3 min. After 6 min, the count rate was observed to be 400. What was its count rate at zero time?
1600
1200
200
2400
Let N = count rate at zero time
N \(\frac{3 min}{\to}\) \(\frac{N}{2}\) \(\frac{3 min}{\to}\) \(\frac{N}{4}\)
\(\frac{N}{4}\)
= 400
N = \(\frac{400}{N/4}\) x N
N = 1600