Two resistances R1 and R2 are made of different materials. The temperature coefficient of the material of R1 is α and of the material of R2 is –β. The resistance of the series combination of R1 and R2 will not change with temperature, if R1/ R2 equals :

(1) αβ

(2) α+βαβ

(3) α2+β2αβ

(4) βα

Subtopic:  Derivation of Ohm's Law |
 57%
From NCERT
PMT - 1997
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An ionization chamber with parallel conducting plates as anode and cathode has 5×107 electrons and the same number of singly-charged positive ions per cm3. The electrons are moving at 0.4 m/s. The current density from anode to cathode is 4μA/m2. The velocity of positive ions moving towards cathode is :

(1) 0.4 m/s

(2) 16 m/s

(3) Zero

(4) 0.1 m/s

Subtopic:  Current & Current Density |
From NCERT
PMT - 1992
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A wire of resistance 10 Ω is bent to form a circle. P and Q are points on the circumference of the circle dividing it into a quadrant and are connected to a Battery of 3 V and internal resistance 1 Ω as shown in the figure. The currents in the two parts of the circle are 

(1) 623A  and  1823A

(2) 526A  and 1526A

(3) 425A  and  1225A

(4) 325A  and  925A

Subtopic:  Combination of Resistors |
 64%
From NCERT
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In the given circuit, it is observed that the current I is independent of the value of the resistance R6. Then the resistance values must satisfy 

(1) R1R2R5=R3R4R6

(2) 1R5+1R6=1R1+R2+1R3+R4

(3) R1R4=R2R3

(4) R1R3=R2R4=R5R6

Subtopic:  Combination of Resistors |
 80%
From NCERT
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In the given circuit, with a steady current, the potential drop across the capacitor must be :

(1) V

(2) V / 2

(3) V / 3

(4) 2V / 3

Subtopic:  Kirchoff's Voltage Law |
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A wire of length L and 3 identical cells of negligible internal resistances are connected in series. Due to current, the temperature of the wire is raised by ΔT in a time t. A number N of similar cells is now connected in series with a wire of the same material and cross–section but of length 2 L. The temperature of the wire is raised by the same amount ΔT in the same time t. The value of N is- 

(1) 4

(2) 6

(3) 8

(4) 9

Subtopic:  Grouping of Cells |
 68%
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What is the equivalent resistance between terminals \(A\) and \(B\) of the network?

        

1. \(\dfrac{57}{7}~\Omega\) 2. \(8~\Omega\)
3. \(6~\Omega\) 4. \(\dfrac{57}{5}~\Omega\)
Subtopic:  Combination of Resistors |
 57%
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The effective resistance between points \(P\) and \(Q\) of the electrical circuit shown in the figure is:

1. \(\frac{2 R r}{\left(R + r \right)}\) 2. \(\frac{8R\left(R + r\right)}{\left( 3 R + r\right)}\)
3. \(2r+4R\) 4. \(\frac{5R}{2}+2r\)
Subtopic:  Combination of Resistors |
 76%
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In the circuit element given here, if the potential at point B, VB = 0, then the potentials of A and D are given as 

(1) VA=1.5V,VD=+2V

(2) VA=+1.5V,VD=+2V

(3) VA=+1.5V,VD=+0.5V

(4) VA=+1.5V,VD=0.5V

Subtopic:  Kirchoff's Voltage Law |
 63%
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The current in a conductor varies with time t as I=2t+3t2 where I is in ampere and t in seconds. The electric charge flowing through a section of the conductor during t = 2 sec to t = 3 sec is :

(1) 10 C

(2) 24 C

(3) 33 C

(4) 44 C

Subtopic:  Current & Current Density |
 88%
From NCERT
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