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1990 - JAMB Physics Past Questions and Answers - page 4

31

Three cells each of e.m.f. 1.5v and an internal resistance of 1.0(\Omega) are connected in parallel across a load resistance of 2.67(\Omega). Calculate the current in the load?

A
0.26A
B
0.41A
C
0.50A
D
0.79A
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32

When a known standard resistor of 2(\Omega) is connected to the 0.0cm end of a meter bridge, the balance point is found to be at 55.0cm. What is the value of the unknown resistor?

A
1.10\(\Omega\)
B
1.64\(\Omega\)
C
2.44\(\Omega\)
D
27.50\(\Omega\)
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33

The total energy required to send a unit positive charge round a complete electrical circuit is the

A
kinetic energy
B
potential difference
C
electromotive force
D
electrical energy
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34

Which of the following is an essential physical property of the wires used for making fuses?

A
low density
B
high thermal conductivity
C
low electrical resistivity
D
low melting point
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35

Which of the following is most suitable for protecting the circuit of 2000W electric iron connected to a 250V mains?

A
13A
B
8A
C
5A
D
3A
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36

Electrical power is transmitted at a high voltage rather than low voltage because the amount of energy loss is reduced due to

A
heat dissipation
B
production of eddy currents
C
excessive current discharge
D
excessive voltage distance
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37

A lamp is rated 240V, 60W. The resistance of the filament is

A
960\(\Omega\)
B
16\(\Omega\)
C
15\(\Omega\)
D
4\(\Omega\)
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38

A 0 - 10mA galvanometer with a coil resistance of 30(\Omega) can be converted to a 0 - 10A ammeter by using

A
0.03\(\Omega\) series resistor
B
0.03\(\Omega\) shunt resistor
C
9.99\(\Omega\) shunt resistor
D
9.99\(\Omega\) series resistor
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39

The number of neutrons contained in the nucleus (^{238}_{92}U) is

A
92
B
146
C
238
D
330
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40

What precaution should a manufacturer take to ensure that energy loss in a transformer is minimized?

A
the winding of the transformer should be made of high resistance wire
B
the core should be made of thin sheets of metal
C
no magnetic material should be used to make the core
D
the flux linking the primary with the secondary coils should be minimum
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