Question

Three 70.0-W, 130-V lightbulbs are connected across a ΔV = 130-V power source, as shown in the figure below. Find the total power delivered to the three bulbs and the potential difference across each. Assume the resistance of each bulb is constant (even though, in reality, the resistance increases markedly with current).

An open circuit begins at a terminal with a wire extending horizontally rightwards until it reaches a lightbulb R₁. After the light bulb, the wire splits downwards into two parallel, vertical branches. The left branch contains a lightbulb R₂ and the right branch contains a lightbulb R₃. The two branches recombine below and the wire extends leftwards until it reaches another terminal below the first. The potential difference across the terminals is ΔV.

(a) Find the total power delivered to the three bulbs.
W

(b) Find the potential difference across each bulb.

ΔVR1 =	V
ΔVR2 =	V
ΔVR3 =	V

Answer 1

The answers are

Bou ,70w, as euch bulb is rated Ri= R2 = R3 = x - 1302 y = 70 a) = 241.42 e To find total power we have to calculate total resistance. Raf R3 are connected in parallel. R23 = xt1542 41.42. :: R23 = 120.7 2 Rnet - Rit R23 [series] = 241.427120.7 = 362.14 12

delivered, ... Net power - P = V2 = 1302 362.14 - 46.67 W (Ans) b) P.d. across enel bulb Net current , I = amet pentades 130 362.14 = 0.36A This current flows through Rias it is connected in series. After passing through Rp this current splits into two, I's the 0.18 A

R2 af R3. which pass through pid aor each bulb is given by, AVR, = I R = 0.36x 241:42 =86.au Cans) AN2 = I R2 = 0.18x241.42 = 43.45 V Cons) AVR3 I' R3 -0.18 x 241.42 = 43.45N Cans).