1.
The smallest resistance that can be obtained by the combination of n resistors each resistance r is :
A
r/n
B
nr
C
r
D
n2r
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The smallest resistance that can be obtained by the combination of n resistors each resistance r is :
r/n
nr
r
n2r
By increasing the temperature, the specific resistance of a conductor and semiconductor
Increases for both
Decreases for conductor, increases for semiconductor
Increases, decreases
Decreases for both
Which of the following has a negative temperature coefficient of resistance ?
Tungsten
Carbon
Nichrome
Platinum
When a metal conductor connected to left gap of a meter bridge is heated, the balancing point
shifts towards right
shifts towards left
remains unchanged
remains at zero
Two wires of the same material are given. The first wire is twice as long as the second and has twice the diameter of the second. The resistance of the first will be
Twice of the second
Half of the second
Equal to the second
Four times of the second
Two equal resistors are connected in series across a battery and consume a power of P. If these are connected in parallel, then the power consumed will be:
2P
4P
p4
P
Two conductors of equal length and radii the ratio of 2 : 3 are; connected in parallel the source of electricity. The ratio of the velocity of electrons in the conductor be :
2 : 3
4 : 9
1 : 1
3 : 2
The specific resistance of a rod of copper as compared to that of thin wire of copper is :
less
more
same
depends upon the length and area of cross-section of the wire
The resistivity of alloy manganin is
Nearly independent of temperature
Increases rapidly with increase in temperature
Decreases with increase in temperature
Increases rapidly with decrease in temperature
The internal resistance of a cell of emf 12 V is 5 x 10-2C Ω. It is connected across an unknown resistance. Voltage across the cell, when a current of 60 A is drawn from it, is
15 V
12 V
9 V
6 V
The example of a non-ohmic resistance is:
copper wire
fi lament lamp
carbon resistor
diode
The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then
The resistance will be halved and the specific resistance will be doubled
The resistance and the specific resistance, will both remain unchanged
The resistance will be doubled and the specific resistance will be halved
The resistance will be halved and the specific resistance will remain unchanged
The drift velocity does not depend upon
Cross-section of the wire
Length of the wire
Number of free electrons
Magnitude of the current
The charge flowing in a conductor varies with time as: q = αt +1/2 βt2 + 16 γt3 Where α, β, γ are positive constants. Then the initial current (l) is given by the condition :
l = α
l = α2
l = α-1
None of these
Suppose H1 is the heat generated per second in the filament of a 100 W, 250 V lamp and is the heat generated in the filament of a 200 W, 250 V lamp. Then H1/ is equal to:
1
2
2-Jan
4-Jan
Siemen is the unit of:
resistance
conductance
specific conductance
None of these
Kirchoff's first and second laws in the electricity are the laws respectively of
Energy and Momentum conservation
Momentum and charge conservation
Mass and charge conservation
Charge and energy conservation
Kirchhoffs first and second laws for electrical circuits are consequences of:
conservation of energy
conservation of electrical charge and energy respectively
conservation of electric charge
neither conservation of energy nor electric charge
In parallel combination of n cells, we obtain
more voltage
more current
less voltage
less current
In an experiment with potentiometer, null point with a cell is found at 240 cm. When the cell is shunted with a resistance 2 Ω, the null point becomes 120 cm internal resistance of cell is :
4 Ω
2 Ω
1 Ω
12 Ω