Topic 2 - Controlling And Using Electric Current

Question 1

What is the unit for current?

Answer 1

Amps, A

Question 2

What is voltage?

Answer 2

The driving force that pushed the current round. Electrical pressure.

Question 3

What is the unit for voltages

Answer 3

Volts, V

Question 4

What is resistance?

Answer 4

Anything in the circuit which slows the flow down.

Question 5

What unit is resistance?

Answer 5

Ohm; Ω

Question 6

What is potential difference?

Answer 6

Voltage/electrical pressure/energy transferred per unit charge passed.

Question 7

What happens to charge when it ‘falls’ through a voltage drop?

Answer 7

It gives up energy

Question 8

How many volts is 1joule/coulomb

Answer 8

1 volt

Question 9

What happens to current at a junction?

Answer 9

It is conserved. Currents doesn’t get used up or lost in a circuit so current at a junction is conserved. Total current entering a junction is equal to the total current leaving a junction.

Question 10

What’s the formula for resistance?

Answer 10

Voltage = current x resistance

Question 11

Describe an experiment you can do to investigate resistant

Answer 11

Set up a standard circuit (with a component voltmeter and ammeter) measure the current and voltage. Ammeter must be placed in series. Voltmeter must be placed in parallel with the component. As you vary the variable resistor it alters current. Record all your readings and plot them on a V-I graph

Question 12

What type of resistor does this graph represent?

Answer 12

Fixed resistors

Question 13

What type of resistor does this graph reprisent?

Answer 13

Filament lamp

Question 14

What type of resistor does this graph represent?

Answer 14

Diode

Question 15

What type of resistor is this?

Answer 15

Light-Dependent Resistor (LDR). This is a special type off resistor that changes it’s resistance depending on how much light there is: in bright light resistance falls. In darkness resistance is highest.

Question 16

What type of resistance is this

Answer 16

Thermistor (temperature-dependant resistor). Hot - resistance drops Cool - resistance goes up

Question 17

What is BIRD TURD?

Answer 17

B- Brightness

I- Increase

R- Resistance

D- Decrease

T- Temperature

U- Up

R- Resistance

D- Down

Question 18

Why do resistors get hot?

Answer 18

Energy transfer when electrons collide with ion lattice that makes up the resistor, energy is released as heat.

Question 19

What are the negative effects of the heating effect on resistors?

Answer 19

The hearing effect increases the resistors resistance so less current will flow. Causes circuit to be less efficient. Can cause components in the circuit to melt.

Question 20

What are the positive effects of the heating effect on resistors?

Answer 20

Fuses protect circuits - they melt and break the circuit of the current gets to high Good for heating things (toasters contain a coil of wire wit high resistance. It heats up so much it glows and gives of infrared heat - light bulbs work in a similar way)

Question 21

What is electrical power?

Answer 21

Rate at which an appliance transfers energy

Question 22

What is the formula for power?

Answer 22

Power = volts x current

Question 23

What is the unit for power

Answer 23

Watts, W

Question 24

What is the formula for energy transferred?

Answer 24

Energy transferred = current x voltage x time

Question 25

What is current?

Answer 25

The rate of flow of charge round the circuit. Will only flow through a component if there is voltage across that component.