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Current Electricity

178 Questions Start Allen Test
All Exams Allen
Q26 Allen OHM'S LAW & ELECTRICAL RESISTANCE MCQ
The effective resistance is $\frac{6}{5}\Omega$ , when two wires are joined in parallel. When one of the wire breaks, the effective resistance is 2 ohms. The resistance of the broken wire was:-
A.
$\frac{3}{5}\Omega$
B.
$2\Omega$
C.
$\frac{6}{5}\Omega$
D.
$3\Omega$
Q27 Allen OHM'S LAW & ELECTRICAL RESISTANCE MCQ
At what temperature will the resistance of a copper wire become three times its value at $0^{\circ}$ C? [Temperature coefficient of resistance for copper = $4 \times 10^{-3}$ per ${}^{\circ}$ C] :-
A.
$400^{\circ}$ C
B.
$450^{\circ}$ C
C.
$500^{\circ}$ C
D.
$600^{\circ}$ C
Q28 Allen OHM'S LAW & ELECTRICAL RESISTANCE MCQ
Copper and silicon are cooled from 300 K to 60 K; the specific resistance:-
A.
decreases in copper but increases in silicon
B.
increases in copper but decreases in silicon
C.
increases in both
D.
decreases in both
Q29 Allen OHM'S LAW & ELECTRICAL RESISTANCE MCQ
Two resistances $R_{1}$ and $R_{2}$ are made of different materials. The temperature coefficient of the material of $R_{1}$ is $\alpha$ and that of the material of $R_{2}$ is $-\beta$ . The resistance of the series combination of $R_{1}$ and $R_{2}$ does not change with temperature, then the ratio of resistances of the two wires at $0^{\circ}C$ will be:
A.
$\frac{\alpha}{\beta}$
B.
$\frac{\alpha + \beta}{\alpha - \beta}$
C.
$\frac{\alpha^{2} + \beta^{2}}{\alpha\beta}$
D.
$\frac{\beta}{\alpha}$
Q30 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
A metal wire of resistance R is cut into three equal pieces which are then connected side by side to form a new wire, the length of which is equal to one third of the original length. The resistance of this new wire is:-
A.
R
B.
3R
C.
$\frac{R}{9}$
D.
$\frac{R}{3}$
Q31 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
Three resistances of values 2 Ī©, 3 Ī© and 6 Ī© are to be connected to yield an effective resistance of 4 Ī©. This can be done by connecting:
A.
3 Ī© resistance in series with a parallel combination of 2 Ī© and 6 Ī©
B.
6 Ī© resistance in series with a parallel combination of 2 Ī© and 3 Ī©
C.
2 Ī© resistance in series with a parallel combination of 3 Ī© and 6 Ī©
D.
2 Ī© resistance in parallel with a parallel combination of 3 Ī© and 6 Ī©
Q32 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
What will be the equivalent resistance between the points A and D? A 10 Ī© 10 Ī© 10 Ī© B C 10 Ī© 10 Ī© 10 Ī© D
A.
10 Ī©
B.
20 Ī©
C.
30 Ī©
D.
40 Ī©
Q33 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
In the circuit shown here, what is the value of the unknown resistance R so that the total resistance of the circuit between points 'P' and 'Q' is also equal to R :-
A.
$\ 3\Omega$
B.
$\ \sqrt{39}\Omega$
C.
$\ \sqrt{69}\Omega$
D.
$\ 10\Omega$
Q34 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
The resistance across P and Q in the given figure is
A.
$\frac{\mathrm{R}}{3}$
B.
$\frac{\mathrm{R}}{2}$
C.
$2\mathrm{R}$
D.
$6\mathrm{R}$
Q35 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
The resistance of the circuit between A and B is :
A.
r
B.
0.5r
C.
2r
D.
3r
Q36 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
Thirteen resistances each of resistance R $\Omega$ are connected in the circuit as shown in the figure. The effective resistance between A and B is :-
A.
$\frac{4\mathrm{R}}{3}\Omega$
B.
$2\mathrm{R}\Omega$
C.
$\mathrm{R}\Omega$
D.
$\frac{2\mathrm{R}}{3}\Omega$
Q37 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
The total resistance between x and y in ohms is:-
A.
$1\Omega$
B.
$4\Omega$
C.
$\frac{4}{3}\Omega$
D.
$\frac{2}{3}\Omega$
Q38 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
The resultant resistance of n wires each of resistance r ohms is R, when they are connected in parallel. When these n resistances are connected in series, the resultant resistance will be :-
A.
$\frac{R}{n}$
B.
$\frac{R}{n^{2}}$
C.
nR
D.
$n^{2}R$
Q39 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
For the network of resistance shown in the fig. the equivalent resistance of the network between the points A and B is 18 Ī©. The value of unknown resistance R is :-
A.
8 $\Omega$
B.
10 $\Omega$
C.
16 $\Omega$
D.
24 $\Omega$
Q40 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
In the arrangement of resistances shown below, the effective resistance between points A and B is
A.
20 $\Omega$
B.
30 $\Omega$
C.
90 $\Omega$
D.
110 $\Omega$
Q41 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
In the circuit shown the equivalent resistance between A and B is
A.
R
B.
2R/5
C.
R/3
D.
2R
Q42 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
In the figure the numerical values denote resistances in SI units. The total resistance of the circuit between a & b will be:
A.
12 ohms
B.
24 ohms
C.
15 ohms
D.
6 ohms
Q43 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
Resistors $R_{1}$ and $R_{2}$ have an equivalent resistance of 6 ohms when connected in the circuit shown below. The resistance of $R_{1}$ could be (in $\Omega$ ):
A.
1
B.
5
C.
8
D.
4
Q44 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
Value of current i in the following circuit is :-
A.
13 A
B.
$12 \mathrm{~A}$
C.
9 A
D.
none of the above
Q45 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
The potential difference between X and Y in volts is :-
A.
1
B.
-1
C.
2
D.
-2
Q46 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
If each resistance in the fig. is of 9 Ī© then reading of the ammeter is :-
A.
5 A
B.
8 A
C.
2 A
D.
9 A
Q47 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
If i = 0.25 A in figure, then value of R is :-
A.
$48\Omega$
B.
$12\Omega$
C.
$120\Omega$
D.
$42\Omega$
Q48 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
If the ammeter in the given circuit reads 2 A, the resistance R is :-
A.
1 ohms
B.
2 ohms
C.
3 ohms
D.
4 ohms
Q49 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
The equivalent resistance and potential difference between A and B for the circuit are respectively :-
A.
$4\Omega ,8\mathrm{V}$
B.
$8\Omega ,4\mathrm{V}$
C.
$2\Omega ,2\mathrm{V}$
D.
$16\Omega ,8\mathrm{V}$
Q50 Allen COMBINATION OF RESISTANCES & KIRCHHOFF'S LAW MCQ
For the current loops shown in the figure, Kirchhoff's loop rule for the loops AHDCBA and AHDEFGA yields these equations respectively :-
A.
$-30\mathrm{I}_1 - 41\mathrm{I}_3 + 45 = 0$ and $-30\mathrm{I}_1 + 21\mathrm{I}_2$ $-80 = 0$
B.
$30\mathrm{I}_1 - 41\mathrm{I}_3 + 45 = 0$ and $30\mathrm{I}_1 - 21\mathrm{I}_2 - 80 = 0$
C.
$30\mathrm{I}_1 + 41\mathrm{I}_3 - 45 = 0$ and $-30\mathrm{I}_1 + 21\mathrm{I}_2$ $+80 = 0$
D.
$-30\mathrm{I}_1 - 41\mathrm{I}_3 - 45 = 0$ and $-30\mathrm{I}_1 + 21\mathrm{I}_2$ $-80 = 0$