Core Practical: Investigating & Testing Circuits Flashcards

All 6 cards in this deck

What are the steps of the core practical to investigate p.d., current and resistance for a resistor?

e.g. a fixed $10\,\Omega$ resistor

1. Connect the resistor in series with a cell, ammeter and variable resistor, with a voltmeter across the resistor.
2. Adjust the variable resistor and record about six pairs of current and p.d. readings.
3. Plot current against p.d. and/or calculate $R = V \div I$.

Why should the circuit be switched off between readings in the core practical on current and potential difference?

To stop the component heating up, which would change its resistance.

What are the steps to test that current is the same everywhere in a series circuit?

e.g. two filament lamps in series with a cell

1. Connect the two lamps in series with the cell and an ammeter.
2. Move the ammeter to a different point in the circuit and read the current again.
3. Compare the readings — they should be equal.

When two identical lamps are connected to the same supply, are they brighter in series or in parallel?

In parallel — each lamp has the full supply p.d., whereas in series they share it.

Give one way to improve the accuracy of the resistance values found in a circuit investigation.

Repeat the readings at each setting and take a mean.

True or false? Reversing the connections to a fixed resistor reverses the current but gives readings of the same size.

True. A fixed resistor has the same resistance in both directions, so its I–V graph is symmetrical through the origin.