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To work out resistances in series:

RT = R1 + R2 + ....... R1 x R2

To work out resistances in parallel:

RT =

R1 1 when there are more than 2 in parallel:

1 = R1

RT

Q1// Q1

Th The e ffol ollo lowi wing ng ligh lightt b bul ulbs bs ha have ve a resistance of 10Ω. When they are wired together in series what is the total resistance RTOTAL ?

Q3/

In th the ed dia iag gra ram m iis s a circ circui uitt tto o connect a speaker to an amplifier. The amplifier must have a load resistance of 64Ω, but the speaker is only 8Ω. What value must the resistor R be to produce a total of 64 Ω ?

Am me eter ter n ne eeds to h ha ave a 30Ω resistor in series with it. The nearest preferred value is 33Ω. What value must resistor R equal when in parallel with the other, to produce a total resistance of 30Ω ?

R2 1

+

R2

1 +

R3

.......

RTOTAL

If the bulbs are now wired in parallel, what will be the value of RTOTAL ?

Q2// Q2

+

or

RTOTAL

R From amplifier

Total resistance must equal 64Ω

Speaker 8Ω

33 Ω

30 Ω Test probes

R Meter

240Ω

Q4// Q4

Tr Try y an and d wo work rk ou outt tthe he to tota tall resistance of this network between A & B? (Tip: Pair similar values)

40Ω A

240Ω

B 80Ω

120Ω PTD - 96

40Ω

Answers

Q1/

a) 2 20 0 ohms b) 5 ohms

Q2/

56 ohms

Q3/

330ohm s

Q4/

100 ohms