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2003 Section 2 Question 17

17) E

You need to learn electricity equations which link power, current, voltage, energy and charge. Also, you need to learn the units of each measurement.

Let us look at the options:

joules/coulombs = Energy/Charge
We know the formula, Energy=Charge x Voltage
Hence, Voltage = Energy/Charge

amperes x ohms = Current x Resistance
We know V=IR which is Voltage = Current x Resistance

watts/amperes = Power/Current
We know P=VI which Power = Voltage x Current
Rearranging, we get Voltage = Power/Current

watts x ohms = √Power x Resistance
We know:
P = VI and I = V/R
If we substitute I = V/R in P=VI, we get:
V² = PR
V= √Power x Resistance

The given units cannot be used to manipulate equations.

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