P2a Topic 2 - Controlling and Using Electric Current

Question 1

Voltage is

Answer 1

The driving force that pushes the current round. Kind of like “electrical pressure”.
Unit: volt, V.

Question 2

Resistance is

Answer 2

Anything in the circuit which slows the flow down.

Unit: ohm

Question 3

If you increase the voltage

Answer 3

Then more current can flow!

Question 4

Potential different is

Answer 4

The energy transferred per Unit Charge Passed

Question 5

1 Volt =

Answer 5

1 joule/coulomb

Question 6

Current is ___________ at a junction

Answer 6

Conserved!

Question 7

An ammeter

Answer 7

Measures the current (in amps) flowing through the component

Question 8

An ammeter must be

Answer 8

Placed in series!

Question 9

A voltmeter

Answer 9

Measures the voltage or potential difference (in volts) across the component

Question 10

A voltmeter must be

Answer 10

Placed in parallel!

Question 11

Fixed resistors: what is the graph like

Answer 11

The current through a resistor (at constant temperature) is proportional to voltage. Different resistors have different resistance, hence different gradients of lines on the graph.

Question 12

Filament lamp: what is the graph like

Answer 12

As the temperature of the filament increases, the resistance increases, hence the graph is a curve.

Question 13

Diode: what is the graph like

Answer 13

Current will only flow through the diode in one direction

Question 14

Potential difference=

Answer 14

Current TIMES BY Resistance

Question 15

A light- dependant resistor or LDR is a special type of resistor that

Answer 15

Changes its resistance based on how much light there is

Question 16

LDR: what happens in bright light

Answer 16

The resistance falls

Question 17

LDR: what happens in darkness

Answer 17

The resistance is highest

Question 18

A thermistor is like an LDR - but it’s resistance depends on

Answer 18

Temperature

Question 19

What happens to resistors when electric current passes through them

Answer 19

1) When there is an electric current in the resistor there is an energy transfer which heats the resistor.
2) This energy transfer is due to the electrons colliding with the ions in the lattice that make up the resistor as they move through it.
3) These collisions give the ions in the lattice extra energy, which is emitted as heat. This heating effect increases the resistor’s resistance - so less current will flow, or a greater voltage will be needed to produce the same current.

Question 20

Electrical power=

Answer 20

Potential difference TIMES BY current

Question 21

Energy transferred=

Answer 21

Current TIMES BY potential difference TIMES BY time

Question 22

Current is

Answer 22

Rate of flow of charge round a circuit. Current will only flow through a component if there is a voltage across that component.
Unit: ampere, A.