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2004 10 questions

Q1072004 · 24 Apr 2004 · Shift 1
1. A. $4 A$
2. B. $2 A$
3. C. $1 A$
4. D. $6 A$
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Answer: A
Q1082004 · 24 Apr 2004 · Shift 1
The resistance of the series combination of two resistances is $S$ . When they are joined in parallel the total resistance is $P$ . If $S = n P$ then the minimum possible value of $n$ is
1. A. $2$
2. B. $3$
3. C. $4$
4. D. $1$
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Answer: C
Q1092004 · 24 Apr 2004 · Shift 1
An electric current is passed through a circuit containing two wires of the same material, connected in parallel. If the lengths and radii are in the ratio of $\frac{4}{3}$ and $\frac{2}{3}$ , then the ratio of the current passing through the wires will be
1. A. $8/9$
2. B. $1/3$
3. C. $3$
4. D. $2$
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Answer: B
Q1102004 · 24 Apr 2004 · Shift 1
In a meter bridge experiment null point is obtained at $20 cm$ , from one end of the wire when resistance $X$ is balanced against another resistance $Y$ . If $X < Y$ , then where will be the new position of the null point from the same end, if one decides to balance a resistance of $4 X$ against $Y$
1. A. $40 cm$
2. B. $80 cm$
3. C. $50 cm$
4. D. $70 cm$
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Answer: C
Q1152004 · 24 Apr 2004 · Shift 1
The Kirchhoff's first law $(\sum i = 0)$ and second law $(\sum i R = \sum E)$ , where the symbols have their usual meanings, are respectively based on
1. A.conservation of charge, conservation of momentum
2. B.conservation of energy, conservation of charge
3. C.conservation of momentum, conservation of charge
4. D.conservation of charge, conservation of energy
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Answer: D
Q1162004 · 24 Apr 2004 · Shift 1
A material $^{'} B^{'}$ has twice the specific resistance of $^{'} A^{'}$ . A circular wire made of $^{'} B^{'}$ has twice the diameter of a wire made of $^{'} A^{'}$ . Then for the two wires to have the same resistance, the ratio $l_{B} / l_{A}$ of their respective lengths must be
1. A. $1$
2. B. $\frac{1}{2}$
3. C. $\frac{1}{4}$
4. D. $2$
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Answer: D
Q1252004 · 24 Apr 2004 · Shift 1
In an $L C R$ series $a . c .$ circuit, the voltage across each of the components, $L, C$ and $R$ is $50 V$ . The voltage across the $L . C$ combination will be :
1. A. $100 V$
2. B. $502$
3. C. $50 V$
4. D. $0 V$ (zero)
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Answer: D
Q1262004 · 24 Apr 2004 · Shift 1
A coil having $n$ turns and resistance $R Ω$ is connected with a galvanometer of resistance $4 R Ω$ . This combination is moved in time $t$ seconds from a magnetic field $W_{1}$ weber to $W_{2}$ weber. The induced current in the circuit is
1. A. $\frac{( W _{2} - W _{1} )}{R n t}$
2. B. $- \frac{n ( W _{2} - W _{1} )}{5 R t}$
3. C. $- \frac{( W _{2} - W _{1} )}{5 R n t}$
4. D. $- \frac{n ( W _{2} - W _{1} )}{R t}$
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Answer: B
Q1272004 · 24 Apr 2004 · Shift 1
In a uniform magnetic field of induction $B$ a wire in the form of a semicircle of radius $r$ rotates about the diameter of the circle with an angular frequency $ω$ . The axis of rotation is perpendicular to the field. If the total resistance of the circuit is $R$ , the mean power generated per period of rotation is
1. A. $\frac{( B π r ω ) ^{2}}{2 R}$
2. B. $\frac{( B π r ^{2} ω ) ^{2}}{8 R}$
3. C. $\frac{B π r ^{2} ω}{2 R}$
4. D. $\frac{( B π r ω ^{2} ) ^{2}}{8 R}$
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Answer: B
Q1392004 · 24 Apr 2004 · Shift 1
A piece of copper and another of germanium are cooled from room temperature to $77 K$ , the resistance of
1. A.copper increases and germanium decreases
2. B.each of them decreases
3. C.each of them increases
4. D.copper decreases and germanium increases
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Answer: D