Topic 2 - Controlling and Using Electric Current Flashcards Preview

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Flashcards in Topic 2 - Controlling and Using Electric Current Deck (32):
1

What is current?

Rate of flow of charge around a circuit

2

What does there need to be in a circuit in order for a current to flow?

A voltage across the circuit

3

What is the unit to measure current?

Ampere, A

4

What is voltage?

Potential difference, driving force that pushes current around, like electrical pressure

5

What is the unit to measure voltage?

Volt, V

6

What is resistance?

Anything in the circuit which slows the flow down

7

What is resistance measured in?

Ohm, Ω

8

What happens to current if you increase the voltage?

More current will flow

9

What happens to current if you increase the resistance?

Less current will flow

10

Potential difference is ______ transferred per ____ ______.

Potential difference is energy transferred per unit charge

11

In a circuit, where is the energy supplied to the charge and how does this affect the voltage?

-Power source
-Increases it

12

What causes charge to decrease in a circuit?

When voltage decreases my components in the circuit e.g. resistors

13

If the change in voltage is bigger, how does this affect the amount of energy transferred for a given charge passing through the circuit?

More energy

14

What is 1 volt in joules/coulombs?

1

15

How does current change around a circuit?

It doesn't, current is conserved; the total current entering a junction id = to total current leaving a junction

16

What does an ammeter measure?

The current flowing through the component in amps

17

How should an ammeter be put into the circuit?

In series

18

What does a voltmeter measure?

Voltage/potential difference across the component in volts

19

How should a voltmeter be placed in a circuit?

In parallel around the component under test

20

What is the effect of a variable resistor on the current?

Alters the current flowing through the circuit which can be recorded by ammeter/voltmeter, plot on voltage-current graphs

21

How does a diode affect current?

Current only flows through a diode in one direction

22

How does a filament lamp affect current?

As temp increases, resistance increases

23

What si the relation between current through a resistor and voltage?

Propotional

24

What is the equation linking voltage, current and resistance?

Potential difference = current x resistance

25

How does an LDR affect resistance?

-Light dependent resistor
-Amount of resistance depends on how light it is
-In bright light, resistance falls
-In darkness, resistance higher

26

How does a thermistor affect resistance?

-Temperature dependent resistor
-Hot: resistance drops
-Cold: resistance increases

27

Why do resistors get hot when an electric current passes through them?

-Energy transfer heats resistor
-Energy transfer due to electrons colliding w/ ions in lattice that make up resistor as move through it
-Collisions give ions in lattice extra energy emitted as heat increasing resistor's resistance reducing curent flow (or more voltage for same current); if too hot, no current flows
-Heating causes circuits to be less efficient as energy wasted. Can cause components to melt (circuit stops working)
-Fuses use this effect to protect circuits: melt + break circuit if current gets too high

28

What are the advantages of the heating effect in a resistor?

-Good if you want to heat something
-e.g. toasters
-Current passes through coil, temp. increases so much so it glows + gives off infrared (heat) radiation that cooks bread
-Light bulbs work in similar way

29

How does an appliance with a high power rating transfer energy?

Transfers lots of energy in a short time

30

What is power measured in?

Watts, W

31

What is the equation linking electrical power potential difference and current?

Electrical power = potential difference x current

32

What is the equation linking energy transferred, current, potential difference and time?

Energy transferred = current x potential difference x time