21.
In a Wheatstone's bridge all the four arms have equal resistance R. If the resistance of the galvanometer arm is also R, the equivalent resistance of the combination as seen by the battery is
A
R/2
B
R
C
2R
D
R/4
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In a Wheatstone's bridge all the four arms have equal resistance R. If the resistance of the galvanometer arm is also R, the equivalent resistance of the combination as seen by the battery is
R/2
R
2R
R/4
In a Wheatstone bridge if the battery and galvanometer are interchanged then the deflection in galvanometer will
change in previous direction
not change
change in opposite direction
none of these.
In a potentiometer of 10 wires, the balance point is obtained on the 7th wire. To shift the balance point to 9th wire, we should
decrease resistance in the main circuit.
increase resistance in the main circuit.
decrease resistance in series with the cell whose emf is to be measured.
increase resistance in series with the cell whose emf is to be determined.
If n cells each of emf e and internal resistance r are connected in parallel, then the total emf and internal resistance will be
ε, r/n
ε, nr
n ε, r/n
n ε, nr
If a certain piece of copper is to be shaped into a conductor of minimum resistance, its length (L) and cross-sectional area shall respectively be :
L, 2A
L/2, 2A
2L, 2A
2l, A/2
For a metallic wire, the ratio V/i (V = the applied potential difference, i = current flowing) is
Independent of temperature
Increases as the temperature rises
Decreases as the temperature rises
Increases or decreases as temperature rises, depending upon the metal
Calculate the amount of charge flowing in 2 minutes in a wire of resistance 10 ? when a potential difference of 20 V is applied between its ends
120 C
240 C
20 C
4C
At what temperature will the resistance of a copper wire become three times its value at 00C? (Temperature coefficient of resistance for copper = 4 x 10-3 peroC)
400oC
450oC
500oC
550oC
An electric heating element consumes 500 W, when connected to a 100 V line. If the line voltage becomes 150 V, the power consumed Will be:
500 W
750 W
1000 W
1125 W
An electric heater is connected to the voltage supply. After few seconds, current gets its steady value then its initial current will be
equal to its steady current
slightly higher than its steady current
slightly less than its steady current
zero
A wire of resistance 3 Ω is cut into three pieces, which are then joined to form a triangle. The equivalent resistance between any corners of the triangle is :
2/3 Ω
3/2 Ω
1/2 Ω
1/3 Ω
A uniform w ire connected across a supply produces heat H per second. If wire is cut into three equal parts and all the parts are connected in parallel across the same supply, the heat produced per second will be :
H/9
9 H
3 H
H3
A steady current flows in a metallic conductor of non-uniform cross-section. The quantities/quantity constant along the length of the conductor is/are
Current, electric field and drift speed
Drift speed only
Current and drift speed
Current only
A cell of emf E is connected with an external resistance R, then p.d. across cell is V. The internal resistance of cell will be
(E-V)R/E
(E-V)R/V
(V-E)R/V
(V-E)R/E
A carbon resistance is having a following coding green, orange, black, gold. The resistance of resistor is
53 x 100 ± 5%
53 x 101 ± 5%
53 x 100 ± 10%
53 x 10 ± 10%
A 5A fuse wire can with stand a maximum power of 1W in circuit. The resistance of the fuse wire is:
0.2 Ω
5 Ω
0.4 Ω
0.04 Ω
If a power of 100 watt is being supplied across a potential difference of 200 V, current flowing is
2A
0.5 A
4.1666666666666664E-2
20 A