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Current Electricity

178 Questions Start Allen Test
All Exams Allen
Q101 Allen MEASURING DEVICES MCQ
A 1 Ω voltmeter has a range of 1V. Find the additional resistance which has to be joined with the series in voltmeter to increase the range of voltmeter to 100 V:
A.
10 Ω
B.
$\frac{1}{99}$ Ω
C.
99 Ω
D.
100 Ω
Q102 Allen MEASURING DEVICES MCQ
A galvanometer having a resistance G and current $i_{a}$ flowing in it, produces full scale deflection. If $S_{1}$ is the value of shunt which converts it into an ammeter of range 0 - i and $S_{2}$ is the value of the shunt for the range 0 - 2i. Then the ratio $\frac{S_{1}}{S_{2}}$ will be :-
A.
1
B.
2
C.
$\frac{1}{2}\left(\frac{i-i_{a}}{2i-i_{a}}\right)$
D.
$\left(\frac{2i-i_{a}}{i-i_{a}}\right)$
Q103 Allen PYQ MCQ
Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volts and the average resistance per km is 0.5 Ω. the power loss in the wires is :-
A.
19.2 W
B.
19.2 kW
C.
19.2 J
D.
12.2 kW
Q104 Allen PYQ MCQ
The resistance in the two arms of a meter bridge are 5 Ω and R Ω, respectively. When the resistance R is shunted with an equal resistance, the new balance point is at 1.6 ℓ₁. The resistance ‘R’ is :-
A.
$10 \Omega$
B.
$15 \Omega$
C.
$20 \Omega$
D.
$25 \Omega$
Q105 Allen PYQ MCQ
In an ammeter 0.2% of main current passes through the galvanometer. If resistance of galvanometer is G, then resistance of ammeter will be :-
A.
$\frac{1}{499}G$
B.
$\frac{499}{500}G$
C.
$\frac{1}{500}G$
D.
$\frac{500}{499}G$
Q106 Allen PYQ MCQ
Two metal wires of identical dimensions are connected in series. If $\sigma_{1}$ and $\sigma_{2}$ are the conductivities of the metal wires respectively, the effective conductivity of the combination is :-
A.
$\frac{\sigma_{1}\sigma_{2}}{\sigma_{1} + \sigma_{2}}$
B.
$\frac{2\sigma_{1}\sigma_{2}}{\sigma_{1} + \sigma_{2}}$
C.
$\frac{\sigma_{1} + \sigma_{2}}{2\sigma_{1}\sigma_{2}}$
D.
$\frac{\sigma_{1} + \sigma_{2}}{\sigma_{1}\sigma_{2}}$
Q107 Allen PYQ MCQ
A circuit contains an ammeter, a battery of 30 V and a resistance 40.8 ohm all connected in series. If the ammeter has a coil of resistance 480 ohm and a shunt of 20 ohm, the reading in the ammeter will be :-
A.
$1\mathrm{A}$
B.
$0.5\mathrm{A}$
C.
$0.25\mathrm{A}$
D.
$2\mathrm{A}$
Q108 Allen PYQ MCQ
Across a metallic conductor of non-uniform cross section a constant potential difference is applied. The quantity which remains constant along the conductor is:
A.
current
B.
drift velocity
C.
electric field
D.
current density
Q109 Allen PYQ MCQ
A, B and C are voltmeters of resistance R, 1.5 R and 3R respectively as shown in the figure. When some potential difference is applied between X and Y, the voltmeter readings are $V_{A}$ , $V_{B}$ and $V_{C}$ respectively. Then :
A.
$\mathrm{V_A}\neq \mathrm{V_B} = \mathrm{V_C}$
B.
$\mathrm{V_A} = \mathrm{V_B}\neq \mathrm{V_C}$
C.
$\mathrm{V_A}\neq \mathrm{V_B}\neq \mathrm{V_C}$
D.
$\mathrm{V_A} = \mathrm{V_B} = \mathrm{V_C}$
Q110 Allen PYQ MCQ
The potential difference (V_A - V_B) between the points A and B in the given figure is :- (A) I=2A 2Ω +3V - 1Ω V_B B
A.
+6V
B.
+9V
C.
-3V
D.
+3V
Q111 Allen PYQ MCQ
A filament bulb (500 W, 100 V) is to be used in a 230 V main supply. When a resistance R is connected in series, it works perfectly and the bulb consumes 500 W. The value of R is :-
A.
26 Ω
B.
13 Ω
C.
230 Ω
D.
46 Ω
Q112 Allen PYQ MCQ
The resistance of a wire is 'R' ohm. If it is melted and stretched to 'n' times its original length, its new resistance will be :-
A.
$\frac{R}{n}$
B.
$n^{2}R$
C.
$\frac{R}{n^{2}}$
D.
nR
Q113 Allen PYQ MCQ
A set of 'n' equal resistors, of value 'R' each, are connected in series to a battery of emf 'E' and internal resistance 'R'. The current drawn is I. Now, the 'n' resistors are connected in parallel to the same battery. Then the current drawn from battery becomes 10 I. The value of 'n' is:
A.
10
B.
11
C.
20
D.
9
Q114 Allen PYQ MCQ
A battery consists of a variable number 'n' of identical cells (having internal resistance 'r' each) which are connected in series. The terminals of the battery are short-circuited and the current I is measured. Which of the graphs shows the correct relationship between I and n?
A.
B.
C.
D.
Q115 Allen PYQ MCQ
Current sensitivity of a moving coil galvanometer is 5 div/mA and its voltage sensitivity (angular deflection per unit voltage applied) is 20 div/V. The resistance of the galvanometer is
A.
40 Ω
B.
25 Ω
C.
250 Ω
D.
500 Ω
Q116 Allen PYQ MCQ
Six similar bulbs are connected as shown in the figure with a DC source of emf E, and zero internal resistance. The ratio of power consumption by the bulbs when (i) all are glowing and (ii) in the situation when two from section A and one from section B are glowing, will be :
A.
$4:9$
B.
$9:4$
C.
$1:2$
D.
$2:1$
Q117 Allen PYQ MCQ
Which of the following acts as a circuit protection device?
A.
conductor
B.
inductor
C.
switch
D.
fuse
Q118 Allen PYQ MCQ
In the circuits shown below, the readings of the voltmeters and the ammeters will be : Circuit 1 Circuit 2
A.
$V_{2} > V_{1}$ and $i_{1} = i_{2}$
B.
$V_{1} = V_{2}$ and $i_{1} > i_{2}$
C.
$V_{1} = V_{2}$ and $i_{1} = i_{2}$
D.
$V_{2} > V_{1}$ and $i_{1} > i_{2}$
Q119 Allen PYQ MCQ
The reading of an ideal voltmeter in the circuit shown is :
A.
0.6 V
B.
0 V
C.
0.5 V
D.
0.4 V
Q120 Allen PYQ MCQ
The metre bridge shown is in balanced position with $\frac{P}{Q}=\frac{\ell_{1}}{\ell_{2}}$ . If we now interchange the positions of galvanometer and cell, will the bridge work? If yes, what will be balance condition?
A.
yes, $\frac{\mathrm{P}}{\mathrm{Q}} = \frac{\ell_2 - \ell_1}{\ell_2 + \ell_1}$
B.
no, no null point
C.
yes, $\frac{\mathrm{P}}{\mathrm{Q}} = \frac{\ell_2}{\ell_1}$
D.
yes, $\frac{\mathrm{P}}{\mathrm{Q}} = \frac{\ell_1}{\ell_2}$
Q121 Allen PYQ MCQ
A charged particle having drift velocity of $7.5 \times 10^{-4} \, ms^{-1}$ is an electric field of $3 \times 10^{-10} \, Vm^{-1}$ , has a mobility in $m^{2} \, V^{-1} \, s^{-1}$ of:
A.
$2.25 \times 10^{-15}$
B.
$2.25 \times 10^{15}$
C.
$2.5 \times 10^{6}$
D.
$2.5 \times 10^{-6}$
Q122 Allen PYQ MCQ
Which of the following graph represents the variation of resistivity ( $\rho$ ) with temperature (T) for copper?
A.
B.
C.
D.
Q123 Allen PYQ MCQ
A resistance wire connected in the left gap of a metre bridge balances a $10 \Omega$ resistance in the right gap at a point which divides the bridge wire in the ratio 3:2. If the length of the resistance wire is 1.5 m, then the length of $1 \Omega$ of the resistance wire is :
A.
$1. 5 \times 1 0 ^ {- 2}$
B.
$1.0 \times 10^{-2} \mathrm{~m}$
C.
$1. 0 \times 1 0 ^ {- 1}$
D.
$1.5 \times 10^{-1} \mathrm{~m}$
Q124 Allen PYQ MCQ
For the circuit shown in the figure, the current I will be
A.
$0.75\mathrm{A}$
B.
$1\mathrm{A}$
C.
$1.5\mathrm{A}$
D.
$0.5\mathrm{A}$
Q125 Allen PYQ MCQ
For the circuit given below, the Kirchhoff's loop rule for the loop BCDEB is given by the equation
A.
$-\mathrm{i}_2\mathrm{R}_2 + \mathrm{E}_2 - \mathrm{E}_3 + \mathrm{i}_3\mathrm{R}_1 = 0$
B.
$\mathrm{i}_2\mathrm{R}_2 + \mathrm{E}_2 - \mathrm{E}_3 - \mathrm{i}_3\mathrm{R}_1 = 0$
C.
$\mathrm{i}_2\mathrm{R}_2 + \mathrm{E}_2 + \mathrm{E}_3 + \mathrm{i}_3\mathrm{R}_1 = 0$
D.
$-\mathrm{i}_2\mathrm{R}_2 + \mathrm{E}_2 + \mathrm{E}_3 + \mathrm{i}_3\mathrm{R}_1 = 0$