P2 - Resistors

What is a resistor?

A component that is used to add resistance to a circuit

What is the symbol for a resistor?

A rectangle (—[ ]—)

Why might we use a resistor in a circuit?

To reduce the current or control the brightness of a component like a lamp

What does resistance tell us?

The potential difference needed to drive a current through a component

What is the equation for resistance?

Resistance (Ω) = Potential difference (V) ÷ Current (A)

What is the unit for resistance?

Ohm (Ω)

What happens when you increase resistance in a circuit?

It becomes harder for current to flow and less energy reaches the components

Why might a resistor be used in series with a lamp?

To share the potential difference and make the lamp dimmer

In a series circuit, how is potential difference shared?

It is shared between all components

What happens to a lamp when a resistor is added in series?

The lamp becomes dimmer because it receives less potential difference

What is an ohmic conductor?

A component in which current is directly proportional to potential difference (if temperature is constant)

What does the current-voltage (I-V) graph of an ohmic conductor look like?

A straight line through the origin

What does a straight-line I-V graph indicate?

That resistance is constant and current is proportional to potential difference

What condition must stay the same for a resistor to behave as an ohmic conductor?

The temperature must remain constant

What happens to the current when the potential difference across an ohmic resistor is increased?

The current increases proportionally

Why does current equal zero when potential difference is zero?

Because there is no energy to push the electrons through the resistor

Is resistance always constant for all components?

No, only for ohmic conductors at constant temperature

If a resistor has V

10 V and I = 0.1 A, what is its resistance? = 100 Ω

What happens to resistance if the temperature of the resistor increases?

The resistance may increase due to more collisions in the conductor

How do electrons lose energy in a resistor?

They collide with atoms, transferring electrical energy into thermal energy

Why is resistance sometimes considered useful?

Because it allows us to control the current in a circuit