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2012 13 questions

Q312012 · 26 May 2012 · Shift 1
The electrical resistance $R$ of a conductor of length $l$ and area of cross section $a$ is given by $R = \frac{ρl}{a}$ where ' $ρ$ ' is the electrical resistivity. What is the dimensional formula for electrical conductivity ' $σ$ ' which is reciprocal of resistivity?
1. A. $[M^{- 1} L^{- 3} T^{3} A^{2}]$
2. B. $[M L^{- 3} T^{- 3} A^{2}]$
3. C. $[M L^{3} T^{- 3} A^{- 2}]$
4. D. $[M^{- 2} L^{3} T^{2} A^{- 1}]$
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Answer: A
Q322012 · 26 May 2012 · Shift 1
1. A.
2. B.
3. C.
4. D.
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Answer: D
Q472012 · 26 May 2012 · Shift 1
The resistance of a wire is $R$ . It is bent at the middle by $18 0^{\circ}$ and both the ends are twisted together to make a shorter wire. The resistance of the new wire is
1. A. $2 R$
2. B. $R /2$
3. C. $R /4$
4. D. $R /8$
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Answer: C
Q592012 · 26 May 2012 · Shift 1
In an experiment of potentiometer for measuring the internal resistance of primary cell a balancing length $ℓ$ is obtained on the potentiometer wire when the cell is open circuit. Now the cell is short circuited by a resistance $R$ . If $R$ is to be equal to the internal resistance of the cell the balancing length on the potentiometer wire will be
1. A. $ℓ$
2. B. $2 ℓ$
3. C. $ℓ /2$
4. D. $ℓ /4$
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Answer: C
Q452012 · 12 May 2012 · Shift 1
Three resistors of $4 Ω, 6 Ω$ and $12 Ω$ are connected in parallel and the combination is connected in series with a $1.5 V$ battery of $1 Ω$ internal resistance. The rate of Joule heating in the $4 Ω$ resistor is
1. A. $0.55 W$
2. B. $0.33 W$
3. C. $0.25 W$
4. D. $0.86 W$
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Answer: C
Q462012 · 12 May 2012 · Shift 1
In a sensitive meter bridge apparatus the bridge wire should possess
1. A.high resistivity and low temperature coefficient.
2. B.low resistivity and high temperature coefficient.
3. C.low resistivity and low temperature coefficient.
4. D.high resistivity and high temperature coefficient.
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Answer: A
Q482012 · 12 May 2012 · Shift 1
1. A. $0.6 T$ and directed out of page
2. B. $1.2 T$ and directed into the plane of page
3. C. $0.6 T$ and directed into the plane of page
4. D. $1.2 T$ and directed out of page
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Answer: A
Q492012 · 12 May 2012 · Shift 1
1. A.6
2. B.4
3. C.2
4. D.8
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Answer: C
Q502012 · 12 May 2012 · Shift 1
A resistance $R$ and a capacitance $C$ are connected in series to a battery of negligible internal resistance through a key. The key is closed at $t = 0$ . If after $t sec$ the voltage across the capacitance was seven times the voltage across $R$ , the value of $t$ is
1. A. $3 R C ln 2$
2. B. $2 R C ln 2$
3. C. $2 R C ln 7$
4. D. $3 R C ln 7$
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Answer: A
Q562012 · 12 May 2012 · Shift 1
This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: A pure semiconductor has negative temperature coefficient of resistance. Statement 2: On raising the temperature, more charge carriers are released into the conduction band.
1. A.Statement 1 is false, Statement 2 is true.
2. B.Statement 1 is true, Statement 2 is false.
3. C.Statement 1 is true, Statement 2 is true, Statement 2 is not a correct explanation of Statement 1.
4. D.Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation of Statement 1.
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Answer: D
Q592012 · 12 May 2012 · Shift 1
1. A.
2. B.
3. C.
4. D.
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Answer: C
Q492012 · 7 May 2012 · Shift 1
This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: The possibility of an electric bulb fusing is higher at the time of switching ON. Statement 2: Resistance of an electric bulb when it is not lit up is much smaller than when it is lit up.
1. A.Statement 1 is true, Statement 2 is false
2. B.Statement 1 is false, Statement 2 is true, Statement 2 is not a correct explanation of Statement 1.
3. C.Statement 1 is true, Statement 2 is true, Statement 2 is a correct explanation of Statement 1.
4. D.Statement 1 is false, Statement 2 is true.
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Answer: C
Q522012 · 7 May 2012 · Shift 1
1. A.800 V, 8 A
2. B.110 V, 1.1 A
3. C.300 V, 3 A
4. D.220 V, 2.2 A
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Answer: D