Topic 10 - Core Practical

Question 1

Outline the basic steps of the practical: investigating relationship between p.d, current and resistance for a resistor and a filament lamp

Answer 1

1) set up circuit with a voltmeter attached in parallel to a resistor and an ammeter attached in series to the resistor
2) Start on a low voltage and slowly increase the voltage, recording the potenial difference and current values each time
3) Repeat, swapping the resistor for a filament lamp
4) plot a graph of current against p,d for both components

Question 2

Draw diagram of the setup

Answer 2

Question 3

Meters needed and their connection:

Answer 3

Voltmeter: connected in parallel to the component
Ammeter: connected in series with the component

Question 4

What component can you use to alter p,d if not using a variable power pack?

Answer 4

A rheostat, variable resistor

Question 5

What must be kept constant to get valid results? How is it dome

Answer 5

Temperature, so resistance of components isnt affected. You should disconnect the supply when not taking readings to avoid unnecessary heating.

Question 6

How do you determine the resistance of a component from an I-V graph?

Answer 6

The resistance at a given point is the inverse of the gradient of the line drawn from that point to the origin.

Question 7

I-V of a fixed resistor

Answer 7

Question 8

I-V graph of a filament lamp

Answer 8

Question 9

What happens to the resistance of a filament lamp as the temperature increases? Why?

Answer 9

Resistance increases
Ions in metal have more energy, so vibrate more, causing more collisions with electrons as they flow through the metal, creating greater resistance to current flow.

Question 10

Outline basic steps of practical: Testing series and parallel circuits using resistors and filament lamps

Answer 10

1) set up a circuit with two filament lamps in series, each with a voltmeter attached over them and an ammeter in series with them.
2) start on a low voltage and slowly increase the voltage, recording the potential difference and current values each time.
3) set up a second circuit with two lamps in parallel and once again record the potential difference and current values for increasing voltages
4) compare the two arrangements

Question 11

Draw circuit diagram for the series arrangement

Answer 11

Question 12

Draw a circuit diagram for the parallel arrangement

Answer 12

Question 13

Which lamp arrangement would you except to have the greatest total resistance?

Answer 13

The two lamps in series will have a greater total resistance than the two lamps in parallel

Question 14

How would the total resistance of the parallel combination, compare to the lamps’ individual resistances?

Answer 14

The total resistance will be smaller than the smallest individual resistance

Question 15

Safety precautions using a filament bulb

Answer 15

Avoid touching them when switched on since they can get very hot
Be careful not to use too high a voltage to avoid blowing the filament