CBSE
Multiple Choice QuestionsA wire of resistance R is elongated n-fold to make a new uniform wire. The resistance of new wire
nR
n2R
2nR
2n2R
Short Answer TypeA battery of emf E and internal resistance r is connected across a pure resistive device (such as an electric heater) of resistance R. Prove that the power output of the device will be maximum if R = r.
Multiple Choice QuestionsA wire of resistance 5 Ω is drawn out so that its new length is 3 times its original length. What is the resistance of the new wire ?
45 Ω
15 Ω
5/3 Ω
5 Ω
Short Answer TypeTwo cells each of same emf e but of internal resistances r1 and r2 are connected in series through an external resistance R. If the potential difference between the ends of the first cell is zero, what will be the value of R in terms of r1 and r2 ?
Multiple Choice QuestionsAn electrical cable having a resistance of 0.2 Ω delivers 10 kW at 200 V DC to a factory. What is the efficiency of transmission ?
65 %
75 %
85 %
95 %
The resistance across A and B in the figure below will be
3R
R
None of the above
Five equal resistance, each of resistance R are connected as shown in figure below. A battery of V volt is connected between A and B. The current flowing in FC will be
The reading of the ammeter in the following figure will be
0.8 A
0.6 A
0.4 A
0.2 A
The current flowing through a wire depends on time as I = 3t2 + 2t + 5. The charge flowing through the cross-section of the wire in time from t = 0 to t = 2 s is
22 C
20 C
18 C
5 C
Two identical cells each of emf E and internal resistance r are connected in parallel with an external resistance R. To get maximum power developed across R, the value of R is
R = r
R = 2r
