Electrical Power Flashcards

All 6 cards in this deck

What is the equation linking power, potential difference and current?

$\text{power} = \text{potential difference} \times \text{current}$

$P = VI$

What is the equation linking power, current and resistance?

$\text{power} = (\text{current})^2 \times \text{resistance}$

$P = I^2R$

What is 1 watt equal to in joules and seconds?

1 watt = 1 joule of energy transferred per second.

What are the steps to find the current in a device from its power and potential difference?

e.g. a 2300 W heater on a 230 V supply

1. Use $P = VI$: $2300 = 230 \times I$
2. Rearrange: $I = P \div V = 2300 \div 230$
3. $I = 10$ A

What are the steps to find the resistance of a component from its power and current?

e.g. a component dissipating 8 W with a current of 2 A

1. Use $P = I^2R$: $8 = 2^2 \times R$
2. Rearrange: $R = P \div I^2 = 8 \div 4$
3. $R = 2\ \Omega$

True or false? Doubling the current in a fixed resistor doubles the power dissipated.

False. Power quadruples, because $P = I^2R$ and the current is squared.