# P2.3 Currents In electrical circuits Flashcards

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1
Q

How do insulating materials become electrically charged?

A
• Charge builds up when two insulators rub together - Electrons leave one surface, leaving it positive. - The other surface gets an equal negative charge - The two oppositely charged surfaces are then attracted together
2
Q

What substance do electrons move easily through?

A

Metals

3
Q

What substance do ions move easily through?

A

Solution

4
Q

Define ‘current’

A

A flow of charge

5
Q

What is the relationship between the size of the current and the rate of the flow of charge?

A

They are the same

6
Q

Define ‘potential difference’

A

Work done per coulomb of charge as it passes between two points

7
Q

Why does the resistance increase as the current goes up in a resistor?

A
• Electrical energy is transferred to heat energy so the resistor gets hot - Causing ions in the conductor to vibrate more - Electrons carrying charge find it hard to move through them so the current can’t move and the resistance increases
8
Q

Why do filament graphs potential difference-current graphs level off?

A
• More current means an increase in temperature - Meaning an increases in resistance - Meaning the current decreases again
9
Q

What is the relationship between current and P.D in a resistor?

A

Current through a resistor is directly proportional to potential difference

10
Q

Why does current only flow in one direction in a diode?

A

The diode has a very high resistance in the opposite direction

11
Q

What is the purpose of a diode in a circuit?

A
• It is used to regulate the potential difference in circuits, by making sure the current can only flow in one direction - It is useful in various electrical circuits
12
Q

How does a thermistor act in a circuit?

A
• To act as a temperature dependent resistor - Hot conditions = resistance drops, current increases - Cold conditions = resistance increases, current decreases
13
Q

Name 3 uses of thermistors and why.

A
• Car engine temperature sensors - Electronic thermostats - Fire alarms By increasing the current at high temperatures, the temperature detector can signal that the temperature is too high.
14
Q

How does a LDR act in a circuit?

A
• It acts as a resistor dependent on light - Bright light = resistance falls - Darkness = resistance increases
15
Q

Name 3 uses of an LDR.

A
• Automatic night lights - Outdoor lighting - Burglar detectors
16
Q

How does an LED act in a circuit?

A
• It emits light when the current flows in a forward direction through it - They indicate the presence of a current in a circuit
17
Q

Why are LEDs being used more as lighting?

A

They use a much smaller current than other forms of lighting.

18
Q

Name 3 uses of LEDs.

A
• Remotes - Traffic lights - Digital clocks
19
Q

What does current do in series?

A

It stays the same for all the components

20
Q

What does current do in parallel circuits?

A

It is split between the devices at a junction

21
Q

What does p.d do in series?

A

It is shared between the components in the circuit

22
Q

What does p.d do in parallel circuits?

A

It stays the same for all the components

23
Q

How are ammeters always connected to a circuit?

A

In series

24
Q

How are voltmeters always connected to a circuit?

A

In parallel with a component

25
Q

Give an example of a real life series circuit.

A

Christmas fairy lights

26
Q

Why is a parallel connection essential in appliances such as cars?

A
• Everything can be turned on and off separately - Everything always gets full voltage from the battery
27
Q

Draw the filament lamp (bulb) symbol

A
28
Q

Draw the cell symbol.

A
29
Q

Draw the open switch symbol

A
30
Q

Draw the fuse symbol

A
31
Q

Draw the resistor symbol.

A
32
Q

Draw the closed switch symbol.

A
33
Q

Draw the thermistor symbol.

A