# Physics - Resistance and Ohm's Law

What is Ohm’s Law?

The current through an ohmic conductor is proportional to the potential difference across it when at a constant temperature.

What is the symbol formula for resistance?

What is the word formula for resistance?

What is the formula for potential difference $V$ in terms of resistance $R$ and current $I$?

What is the formula for current $I$ in terms of resistance $R$ and potential difference $V$?

What are the units for resistance?

Ohms, $\Omega$

What does $1\Omega$ mean?

The resistance of a component when a potential difference of $1V$ is produced per ampere of current.

In an Ohmic conductor, what happens if you double the potential difference?

The current also doubles.

How can you tell from a voltage-current graph that something is an Ohmic conductor?

The line is linear.

How could you describe resistance in a component?

The amount that a component resists the flow of charge carriers through it.

What is the resistance of a component $R$ defined as?

The ratio between $V$ and $I$.

Which of these components is an Ohmic conductor?

B

Which of the components shows a decreasing resistance at higher currents?

A

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What is an Ohmic conductor?

A component where the current is always directly proportional to the potential difference.

What is the threshold voltage in a diode?

The voltage at which a diode starts letting current through.

What component is this?

A resistor.

How can you tell this component in an Ohmic conductor?

The current is directly proportional to the potential difference.

What is the gradient equal to?

What is on the $y$-axis of an $IV$ characteristic?

What is on the $x$-axis on an $IV$ characteristic?

Which graph, left or right, has a higher resistance?

Left.

Why does a smaller gradient mean a larger resistance?

Because the gradient is $\frac{1}{R}$ it’s the opposite to what you expect.

What component is this?

A filament bulb.

How can you tell that this component is not an Ohmic conductor?

The current is not directly proportional to the potential difference.

What happens to resistance as voltage increases?

It begins to increase.

What component is this?

A diode.

Effectively, what is the resistance on the left hand side of the graph?

Is a diode an Ohmic conductor?

No.

What is this circuit used to measure?

How current varies with voltage.

How can you take data for “negative voltages”?

Flip the polarity of the battery.