P2 Electricity

Question 1

What is current?

Answer 1

Flow of electrical charge

Question 2

What needs to be present for electrical charge to flow around a complete circuit?

Answer 2

Potential difference

Question 3

Unit of current

Answer 3

Ampere

Question 4

What needs to be true if the current has the same value everywhere?

Answer 4

A single, closed loop

Question 5

What is volatge

Answer 5

The driving force (potential difference) that pushes the charge around (volts)

Question 6

Resistance

Answer 6

Everything that slows down the flow

Question 7

What factors affect the current?

Answer 7

Potential difference and resistance

Question 8

What is the size of the current?

Answer 8

The rate of flow of charge (more charge passes around the circuit when a larger current flows)

Question 9

Potential difference forumla

Answer 9

V = A * R

Question 10

Ammeter

Answer 10

• Measures the current in amp

- Must always be placed in series with whatever you’re investigating

Question 11

Voltmeter

Answer 11

• Measures the voltage across the test wire

- Must always be placed parallel around whatever you’re investigating

Question 12

Ohmic conductors resistance does not change with (at a constant temperature) …

Answer 12

current

Question 13

When the heat increases, the resistance and current …?

Answer 13

Increases

Question 14

Diodes resistance

Answer 14

• Allow current flow in one direction

- Doesn’t allow current flow in the opposite direction

Question 15

LDR

Answer 15

• Resistor that is dependent on the intensity of light

- Indirectly proportional

Question 16

Thermistor

Answer 16

• A temperature dependent resistor

- Indirectly proportional

Question 17

Why can LDR’s and thermistors be important?

Answer 17

• They can be used to turn on certain circuits

- Conditional dependant

Question 18

Energy transferred depends on?

Answer 18

Power

Question 19

What determines the power of an electrical appliance?

Answer 19

How much energy it transferes per second

Question 20

Energy transferred by electrical work equation

Answer 20

Energy = Power * Time

Question 21

What is a power rating

Answer 21

A label with the maximum safe power that they can operate at

Question 22

What are some downsides to higher power?

Answer 22

• They can be less efficient

- The energy won’t be put to exactly one process (could be sound, or thermal)

Question 23

What is potential difference in terms of charges passed?

Answer 23

Energy transferred

Question 24

Energy transferred J =

Answer 24

Charge * Potential difference

Question 25

Power (W) =

Answer 25

Potential difference * Current

Question 26

National Grid

Answer 26

• A giant system of cables and transformers that cover the UK and connects power stations to consumers
• Transfers electrical power from power stations anywhere on the grid to anywhere else on the grid where it’s needed

Question 27

Why does the national grid use a high Pd and a low current

Answer 27

• A high current loses loads of energy as the wires heat up and energy is transferred to the thermal energy of the surroundings
• Much cheaper and keeps the current power low as possible

Question 28

Transformer

Answer 28

• 2 coils joined with an iron core that increases or decreases the potential difference
• The secondary coil has more turns than the primary coil
• Therefore the current is decreased
• The transformers are practically 100% efficient