P4: Electric circuits

Question 1

What is current

Answer 1

Flow of charge in a circuit

Question 2

What is current measured in

Answer 2

Amperes

Question 3

How do we calculate charge flow

Answer 3

Current X Time

Question 4

How can an electric charge be able to flow

Answer 4

There must be a potential difference source and a closed or complete circuit.

Question 5

What is an electrical conductor

Answer 5

A material that allows electric current (flow of charge) to pass through. It conducts electricity

Question 6

What is an electrical insulator

Answer 6

A material that doesn’t allow electric current (flow of charge) to pass through. It doesn’t conduct electricity. It has no delocalised electrons

Question 7

What is electric current through a metal

Answer 7

Flow of delocalised electrons

Question 8

What is potential difference (voltage)

Answer 8

The pushing force of current in a circuit

Question 9

What is voltage measured in

Answer 9

Volts

Question 10

What do we use to measure current

Answer 10

Ammeter

Question 11

What do we use to measure voltage

Answer 11

Voltmeter

Question 12

What is resistance

Answer 12

The slowing force of current in a circuit

Question 13

What is resistance measured in

Answer 13

Ohms

Question 14

What is the effect linking voltage, current and resistance

Answer 14

If voltage is increased, current is increased and resistance is constant. To measure resistance of a component, measure the voltage of a component. The longer the wire, the higher the resistance.

Question 15

What is the equation to work out resistance

Answer 15

Voltage/Current

Question 16

What are the results if we plot a current voltage graph

Answer 16

As the voltage is increased, the current is increased.

It also obeys Ohms Law as it states it is a straight line. The slope of the graph is 1/resistance. It shows that the resistance is constant.

Question 17

What are the results if we plot a filament bulb graph

Answer 17

The gradient will decrease at larger potential differences. When current through a filament (thin wire) lamp increases, temperature of lamp increases. This increases resistance of the lamp and causes a curve in the graph

Question 18

What is a diode

Answer 18

Diodes are components that allow current to flow in one direction

Question 19

What is a rectifier

Answer 19

Rectifiers are components that turn an alternating current into a direct current.

Diodes act as rectifiers as they break the alternating current when changing direction

Question 20

What is a thermistor

Answer 20

A component where resistance changes with its temperature.

Usually increasing temperature decreases resistance. Thermistors can be used to turn a heater off when a house reaches a certain temperature

Question 21

What is an LDR

Answer 21

Light Dependent Resistor. The resistance changes with light intensity. An LDR can switch lights on when its dark

Question 22

What does the energy source do in an electric circuit

Answer 22

Provides electrical energy to a bulb which radiates that energy as light and heat energy

Question 23

What is an ohmic conductor

Answer 23

A conductor that obeys Ohm’s Law. It has a constant resistance. Current through an ohmic conductor (at constant temperature) is directly proportional to potential difference across a resistor

Question 24

What is a series circuit

Answer 24

A circuit with all its components connected on the same line as each other. In series, current is the same.

Question 25

How do we calculate resistance in a series circuit

Answer 25

Add up all of the individual resistors together

Question 26

How is a battery made

Answer 26

Combining cells

Question 27

How do we calculate voltage in a series circuit

Answer 27

Add up all of the individual voltages together

Question 28

What is a parallel circuit

Answer 28

A circuit that has its components connected in separate branches of wires to the energy source. In parallel, voltage is the same across everywhere.

Question 29

How does current work and how do we work it out in parallel

Answer 29

Current through battery is larger than all of the individual currents. To work out the total current, add all of them up individually. It should equal the total current in the supply.

Question 30

How do we work out the resistance in parallel

Answer 30

The combined resistance of two resistors in parallel is less then the resistance of the resistors individually. To work out the total resistance, deduct the individual resistors together

Question 31

What happens to the lamp in parallel

Answer 31

Each lamp can switched off or on separately. However if 1 lamp breaks, current can still flow through the others.

Question 32

What is the equation for power

Answer 32

Energy transfer/Time

Question 33

What is the other equation for power

Answer 33

Current X Current X Resistance

Question 34

What are two other equations for power

Answer 34

Voltage x Current

Current X Current X Resistance

Question 35

What is Ohms Law?

Answer 35

Current through an ohmic conductor is directly proportional to the voltage across the resistor. This means the resistance remains constant as the current changes