Question

Problem 3:[15]) A light bulb is connected in the circuit shown in the figure with the switch S open. All the connecting leads have no appreciable resistance and the battery has no internal resistance. All resistances including the bulb have R=20 Ohms and the battery voltage is 1do Volts. (a) When the switch S is open and when it is closed, what are the effective resistances of the circuit in both cases? [5] (b) When the switch is open and closed, what are the currents through R in both cases?[5] c) When we close the switch S, which statements below accurately describe the behavior of the circuit? (There may be more than one correct choice.)[5] Bulb TS A) The brightness of the bulb will increase. B) The brightness of the bulb will decrease. C) The brightness of the bulb will not change. D) The potential drop across R2 will decrease. E) The potential drop across R2 will not change.

Answer 1

c)

When the switch s is open then P2 since all Resistance ( Inclueling bulbs are connected in pered series so Rea = Rit Rot R₂ = 20+20+20 Req=tor The switch is closed Now R₂ l Rzare in perralle So Resultant of (Reb Ry) R = R2 XR3 - 20x20 = 400 = R₂ + R3 100 20420 to - 100 from fig e Reg = Rit Rot R = 2042utlo-sor Req=sor When the current switch is open. Since series Resistors have equal so current in Rr. T-V = 100 = 1.67A => I = 1.67A I-Reg 60 When the switch is closed I current in circuit lona 2 Rey so potential drop across R V=IR = 2x10=20v So Curent in Rr I = V = 20 147

When the switch is closed then current in the circuit become 2A (from 1.67 A)

So brightness of the bulb will increase.

When the switch is open then current in R_{​​​​​​2} is 1.67A.

When the switch is closed then current in R2 is 1.0A.

So According to the ohm's law (V=IR ).

The potential drop across R2 will decrease.

Anser are ( A, D).