1997 - JAMB Physics Past Questions and Answers - page 4
31
A galvanometer of internal resistance 50\(\Omega\) has a full scale deflection for a current of 5mA. What is the resistance required to covert it to a voltmeter with full scale deflection of 10V?
A
1750\(\Omega\)
B
1950\(\Omega\)
C
2000\(\Omega\)
D
2500\(\Omega\)
correct option: b
Users' Answers & Comments32
If 8 x 10-2J of work is required to move 100\(\mu\)C of charge from a point X to a point Y in an electrical circuit, the potential difference between X and Y is
A
4.0 x 102 v
B
4.0 x 104 v
C
8.0 x 102 v
D
8.0 x 102 v
correct option: c
V = \(\frac{W}{Q}\)
V = \(\frac{8 \times\ 10^2}{100 \times\ 10^{-6}}\)
V = 8.0 x 102 v
Users' Answers & CommentsV = \(\frac{8 \times\ 10^2}{100 \times\ 10^{-6}}\)
V = 8.0 x 102 v
33
In a meter bridge experiment, two resistor 2\(\Omega\) and 3\(\Omega\) occupy the left and right gaps respectively. Find the balance point from the left side of the bridge
A
20cm
B
40cm
C
60cm
D
80cm
correct option: b
Let the point be x
\(\frac{2}{x}\) = \(\frac{3}{100 - x}\)
making x subject of formula,
2(100 - x) = 3x
200 - 2x = 3x
200 = 3x + 2x
200 = 5x
divide both side by 5
x = 40cm
Users' Answers & Comments\(\frac{2}{x}\) = \(\frac{3}{100 - x}\)
making x subject of formula,
2(100 - x) = 3x
200 - 2x = 3x
200 = 3x + 2x
200 = 5x
divide both side by 5
x = 40cm
34
Two 50\(\mu\)F parallel plate capacitors are connected in series. The combined capacitor is then connected across a 100-V battery. The charge on each plate of the capacitor is
A
5.00 x 10-5C
B
2.50 x 10-3C
C
1.25 x 10-3C
D
1.00 x 10-2C
correct option: b
For series, C = \(\frac{50 \times\ 50}{50 + 50}\)
C= 25\(\mu\)F
Q = CV
Q = 25 x 100 x 10-3
Q = 2.5 x 10-3C
Users' Answers & CommentsC= 25\(\mu\)F
Q = CV
Q = 25 x 100 x 10-3
Q = 2.5 x 10-3C
35
What is the total electrical energy consumed by using an electric cooker rated 1000W for 5 hrs?
A
5.3 x 103J
B
6.5 X 103J
C
1.8 X 107J
D
2.3 X 107J
36
The power dissipated in an a.c. circuit with an r.m.s, current of 5A, r.m.s voltage of 10V and a phase angle of 60o is
A
25W
B
50W
C
120W
D
125W
37
The voltage of the domestic electric supply is represented by the equation V = 311 sin314.2t. Determine the frequency of the a.c. supply [\(\pi\) = 3.142]
A
50.0Hz
B
100.0Hz
C
311.0Hz
D
314.2Hz
correct option: a
V = 311 sin314.2t compare with,
V = V sin2\(\pi\)Ft
2\(\mu\)F = 314.2
F = \(\frac{314.2}{2 \times\ 3.142}\)
F = 50Hz
Users' Answers & CommentsV = V sin2\(\pi\)Ft
2\(\mu\)F = 314.2
F = \(\frac{314.2}{2 \times\ 3.142}\)
F = 50Hz
38
In a purely inductive circuit, the current
A
lags behind the voltage in phase by 90o
B
leads the voltage in phase by 90o
C
is in the same phase with the voltage
D
leads the voltage by 180o
correct option: a
Users' Answers & Comments39
One of the features of the fission process is that
A
its products are not radioactive
B
it leads to chain reaction
C
neutrons are not released
D
the sum of the masses of the reactants equals the sum of masses of the products
correct option: b
Users' Answers & Comments40
The graphite rods surrounding the uranium fuel rods in a nuclear reactor, are used to
A
absorb the neutrons and hence halt the nuclear process
B
create the neutrons and hence slow up the nuclear process
C
slowdown the neutrons and hence slow up the nuclear process
D
speed up the neutrons and hence speed up the nuclear process
correct option: c
Users' Answers & Comments