Resistance Flashcards

All 6 cards in this deck

What is resistance, and what is its unit?

The opposition to the flow of charge (current), measured in ohms ($\Omega$).

What is the equation linking potential difference, current and resistance, with units?

potential difference (V) = current (A) $\times$ resistance ($\Omega$), $V = I \times R$.

What are $V = I \times R$ rearranged to make resistance the subject, and to make current the subject?

$R = \dfrac{V}{I}$ and $I = \dfrac{V}{R}$.

What are the steps to calculate the resistance of a component from meter readings?

e.g. voltmeter reads 6 V, ammeter reads 2 A

1. Write $V = I \times R$: $6 = 2 \times R$
2. Rearrange: $R = \dfrac{V}{I} = \dfrac{6}{2}$
3. Resistance $= 3\,\Omega$

What is a variable resistor used for in a circuit?

To change the resistance of the circuit, and so change the current in it.

True or false? For a fixed potential difference, doubling the resistance halves the current.

True. $I = \dfrac{V}{R}$, so current is inversely proportional to resistance.