2014 - JAMB Physics Past Questions and Answers - page 4
31
If a metal wire 4m long and cross-sectional area 0.8 mm2 has a resistance of 60, find the resistivity of the wire
A
5.3x10-7
B
3.0x10-5
C
1.2x10-6
D
3.2x10-6
correct option: c
\(P = \frac{Ra}{L}\Omega m\)
\(P = \frac{6 \times 0.8}{4}\Omega m\)
\(P = 1.2 \times 10^{-6}\Omega m\)
Users' Answers & Comments\(P = \frac{6 \times 0.8}{4}\Omega m\)
\(P = 1.2 \times 10^{-6}\Omega m\)
32
A circuit has a resistance of 200Ω. The resistance of the circuit can be reduced to 120Ω when
A
A 300Ω resistor is connected to it in parallel
B
An 80Ω resistor is conneceted to it in series
C
A 150Ω resistor is connected to it in parallel
D
A 240Ω resistor is connected to it in series
correct option: a
For parallel resistance,
\(\frac{300 \times 200}{500}\)
\(= 120 \Omega \)
Therefore it is when a 300Ω resistor is connected to it in parallel
Users' Answers & Comments\(\frac{300 \times 200}{500}\)
\(= 120 \Omega \)
Therefore it is when a 300Ω resistor is connected to it in parallel
34
What is the best method of demagnetizing a steel bar magnet?
A
Hammering
B
Heating it
C
Rough handling it
D
Solenoid method
correct option: d
Users' Answers & Comments35
The magnitude of the angle of dip at the equator is
A
360o
B
0o
C
90o
D
180o
correct option: b
Users' Answers & Comments36
When an atom undergoes a beta decay, the atomic number of the nucleus
A
Remains unchanged
B
Decreases by one
C
Increases by one
D
Becomes zero
correct option: c
Users' Answers & Comments37
Calculate the mass of the copper deposited during electrolysis when a current of 4A passes through a copper salt for 2 hours. [Ece of Copper z=3.3x10-7kgC-1]
A
2.9x105kg
B
9.5x10-7kg
C
9.5x10-3kg
D
2.9x104kg
correct option: c
Mass = ZIT kg
Mass = 3.3 x 10-7 x 4 x 2 x 60 x 60 kg
Mass = 9.5 x 10-3kg
Users' Answers & CommentsMass = 3.3 x 10-7 x 4 x 2 x 60 x 60 kg
Mass = 9.5 x 10-3kg
38
Which gas produces a pink coloured light in a discharge tube?
A
Mercury
B
Argon
C
Air
D
Neon
correct option: c
Users' Answers & Comments39
In a common emitter configuration, the output voltage is through the
A
Resistor
B
Base
C
Collector
D
Emitter
correct option: d
Users' Answers & Comments40
When \(^{210}_{82}Pb\) decays to \(^{206}_{80}Pb\), it emits
A
two alpha and two beta particles
B
an alpha particle
C
one beta particle
D
one alpha and one beta particle
correct option: b
Users' Answers & Comments