Current Electricity

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

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

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

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

Kirchhoff'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

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

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 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 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

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?