PAG 3.2 - Investigating Electrical Characteristics

Question 1

How can the current be measured in a component?

Answer 1

An ammeter can be connected in series with the component to measure the current passing through it

Question 2

How can the potential difference across a component be measured?

Answer 2

A voltmeter can be connected in parallel to the component to measure the potential difference across it

Question 3

What is a rheostat?

Answer 3

A component whose resistance can be varied throughout an experiment to produce varying currents

Question 4

State Ohm’s Law

Answer 4

The current flowing though a component is directly proportional to the potential difference across it, assuming constant conditions

Question 5

How can you obtain readings for negative voltages?

Answer 5

Reverse the polarity of your supply across the component

Question 6

Describe the I-V graph from an Ohmic component

Answer 6

Straight line through the origin

Question 7

Describe the I-V characteristic of a diode

Answer 7

Required PD met until current can flow, and resistance will be low (steep gradient)

Question 8

Why should the power source be switched off between readings?

Answer 8

To reduce the heating effect, more accurate results

Question 9

Suggest why the reading given by a voltmeter may differ slightly from the true value

Answer 9

Voltmeter is assumed to have infinite resistance, so assumed that no current is drawn through them. In reality a vary small current is drawn.

Question 10

Suggest why the reading given by an ammeter may differ slightly from the true value?

Answer 10

Ammeters assumed to have 0 resistance, so no voltage drop in them, but in reality a small voltage is dropped

Question 11

Why is it important that the surrounding temperature remains constant when carrying out this experiment?

Answer 11

Temperature change can affect the resistance of the components, which may result in accurate characteristics being observed

Question 12

Why does temperature affect resistance

Answer 12

As temp increases, ions gain kinetic energy and vibrate more, this makes it harder for electrons to flow through the component, so resistance is higher

Question 13

What safety precautions should be taken when carrying out this experiment?

Answer 13

Switch off power supply when not in use
Never touch exposed metal contacts and ensure the voltage being used does not exceed component rating