Question

a.When two resistors RA and RB are combined in series and connected to a battery it is observed that the ratio of the power dissipated in RA to that dissipated in RB is equal to 10. If this arrangement is dismantled and the same two resistors connected in parallel to the same battery, what is the ratio of the power dissipated in RA to that dissipated in RB in this new circuit?

b.How much energy is converted by a 12 W energy-saver light bulb in 25 minutes, and what current does it draw from the 240 V mains for which it is designed?

c.Resistors of resistance 900 Ω and 300 Ω are joined in series across a 24 V supply. What is the potential difference across the 300 Ω resistor and what is the current flowing through it?

d.A network of four 10 Ω resistors comprises a pair of resistors connected in parallel that are connected in series with another pair of resistors that are also connected in parallel. What is the total resistance of this network?

e.A set of Christmas tree lights consists of 30 identical bulbs connected in series. When they are connected to a constant 240 V electricity supply, the set of bulbs dissipates a total of 150 W of electrical power. In an attempt to improve performance, an amateur electrician decides to remove 6 bulbs and replace them with connections of effectively zero resistance. Assuming that the bulbs do not burn out, how much power is dissipated by each bulb when the modified set is switched on?

Answer 1

RA IZKA - 10 I² KB RA= 10kB RA Vita RB - I KA TO PA PB I E = p. t = 12x25x60 (25min = 28x6uve - 18 ooo - 18KJ I= P = 12 2yo = 1 A = Somos 20 900 2 I = 24 12.00 24 y V = IR 100 X300 Voor 17 ++ = 2 2 0 - - - Rp 10 Rp=5 Ronet - 5+5 =lan

of R = Resis fans ce let each 150 = (24012 (PM P' (as 6 bulb remonts (240)2 (24R) 21 > P'= 150x30 i suo 11 12 150 ge 24 8 each bulba P -7.8125W 8X24 power by 24