The figure to the right shows a branch of a larger circuit. A current of 3A flow

Question

The figure to the right shows a branch of a larger circuit. A current of 3A flows through point A in the direction drawn. The reference point for the zero of potential is labelled point B. What is the electric potential at A? The figure shows two light bulbs, B_A and B_B in parallel connected across a battery. When the switch is closed a third bulb, B_C, is connected in parallel with the first two bulbs. Is the current through the battery before the switch is closed, I_before, greater, the same as, or less than the current through the battery after the switch is closed, I_after The figure to the right shows an arrangement of identical resistors in a circuit. With the switch open, a current I flows in the circuit. How much current flows in the circuit if the switch is closed?

Explanation / Answer

9.8 )

Here,

let the potential at point A is VA

Using KVL

VA - 2 * 3 - 1 * 3 - 3 * 3 - VB = 0

VA = 6 + 3 + 9

VA = 18 V

the potential at A is e) 18 V

9.9)

when a new bulb Bc is added to the circuit ,

the overall resistance of circuit will decrease

and the current in battery will increase

Ibefore < Iafter

9.10)

initially , as there are 4 resistances,

I = V/(4*R)

now , after closingthe circuit

new resistance = 2*R,

Inew = V/(2R)

Inew = 2*R

the e) 2*I

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