P4 - Electric Circuits

Question 1

What is current?

Answer 1

The flow of electrical charge

Question 2

What is the unit for current?

Answer 2

Amperes (A)

Question 3

What conditions are compulsory for electrical charge to flow around a circuit?

Answer 3

The circuit needs to be complete
There is a source of potential difference

Question 4

What is potential difference?

Answer 4

The driving force that pushed the charge around the circuit

Question 5

What is potential difference measured in?

Answer 5

Volts (V)

Question 6

What is Resistance?

Answer 6

Anything that slows the flow in the current down

Question 7

What is the unit for resistance?

Answer 7

Ohms

Question 8

What is the relationship between resistance and current in a circuit?

Answer 8

The greater the resistance across a component, the smaller the current the current that flows

Question 9

What is Charge flow measured in?

Answer 9

Coulombs (C)

Question 10

What is the equation that links charge flow, current and time?

Answer 10

Charge flow = current x time

Question 11

What is the formula linking potential difference and current? (Ohms law)

Answer 11

V = IR

Question 12

What does the ammeter measure and what does the voltmeter measure?

Answer 12

Current (amps)
Potential difference (volts)

Question 13

If the resistance is kept constant and the potential difference is increased, what will haooen to the current?

Answer 13

It should increase proportionally

Question 14

What happens when you increase the temperature of a circuit?

Answer 14

The resistance will increase

Question 15

What are diodes?

Answer 15

Devices that only allow current to flow in one direction

Question 16

What does LDR stand for?

Answer 16

Light Dependent Resistor

Question 17

What is a LDR (light dependent resistor?

Answer 17

A resistor with resistance that depends on light intensity

Question 18

What is a thermistor?

Answer 18

A temperature dependent resistor

Question 19

What happens to the resistance of an LDR in Bright light and darkness?

Answer 19

Bright light - resistance is low
Darkness - resistance is high

Question 20

What happens to the resistance in a thermistor in hot and cool conditions?

Answer 20

Hot - the resistance drops
Cool - the resistance increases

Question 21

What is the main difference between a series and a parallel circuit

Answer 21

A series circuit has only one single loop while a parallel circuit has more than 1 loop

Question 22

Why are parallel circuits generally more reliable than series circuits?

Answer 22

If any loop in a parallel circuit breaks, the circuit can still flow

Question 23

How do you carry out the ‘finding the resistance in a series circuit’ practical?

Answer 23

1.Get at least 4 identical resistors
2. Build a series circuit and gradually increase the number of resistors added.
3. Find the voltage of the cell/battery and use the ammeter to measure the current
4. With these, you can calculate the resistance
5. Compare the number of resistors compared to the total resistors

Question 24

What is the ‘National Grid’?

Answer 24

The giant network of transformers and wires that spreads across the country to distribute electricty

Question 25

Where does most of the UKs electricity come from?

Answer 25

Power stations

Question 26

How do power stations work?

Answer 26

They generate alot of heat and then convert the thermal energy to electrical energy

Question 27

What is the equation that links power, voltage and current?

Answer 27

P = V x I

Question 28

Why does a high current generate lots of heat?

Answer 28

Due to the resistance in the wire

Question 29

Why is a high current bad when trying to transfer electricty?

Answer 29

Loses energy to thermal energy

Question 30

How do you make a circuit have a low current?

Answer 30

Increase the voltage

Question 31

What are step up transformers?

Answer 31

A device that increases the voltage in a circuit