CBSE
Multiple Choice QuestionsKirchhoff's first and second laws for electrical circuits are consequences of
conservation of energy
conservation of electric charge and energy respectively
conservation of electric charge
conservation of electric charge
Three resistances P, Q, R each of 2 Ω and an unknown resistance S form the four arms of a Wheatstone's bridge circuit. When a resistance of 6 Ω is connected in parallel to S the bridge gets balanced. What is the value of S?
2 Ω
3 Ω
6 Ω
6 Ω
The resistance of a wire is ‘R’ ohm. If it is melted and stretched to ‘n’ times its original length, its new resistance will be
nR
R/n
n2R
n2R
A set of 'n' equal resistors, of value 'R' each, are connected in series to a battery of emf 'E' and internal resistance 'R'. The current drawn is I. Now, the 'n' resistors are connected in parallel to the same battery. Then the current drawn from battery becomes 10 I. The value of 'n' is
10
11
9
20
In the circuit shown, if a conducting wire is connected between points A and B, the current in this wire will
flow from A to B
flow in the direction which will be decided by the value of V
be zero
be zero
A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F, because the method involves :
Cells
Potential gradients
A condition of no current flow through the galvanometer
A condition of no current flow through the galvanometer
Two cells, having the same emf, are connected in series through an external resistance R. Cells have internal resistances r1 and r2 (r1 > r2) respectively. When the circuit is closed, the potential difference across the first cell is zero, The value of R is
A battery consists of a variable number 'n' of identical cells (having internal resistance 'r' each) which are connected in series. The terminals of the battery are short-circuited and the current I is measured. Which of the graphs shows the correct relationship between I and n?
A carbon resistor of (47 ± 4.7) kΩ is to be marked with rings of different colours for its identification. The colour code sequence will be
Violet – Yellow – Orange – Silver
Yellow – Violet – Orange – Silver
Green – Orange – Violet – Gold
Yellow – Green – Violet – Gold
A steady current of 1.5 A flows through a copper voltameter for 10 min. If the electrochemical equivalent of copper is 30 x 10-5 g C-1, the mass of copper deposited on the electrode will be:
0.40 g
0.50 g
0.67 g
0.67 g
