Unit 2 - Electrical Circuits Flashcards
0
Q
What does a Voltmeter measure?
A
Measures voltage/potential difference (v/volts)
1
Q
What does an ammeter do?
A
Measures current - in amperes (A)
2
Q
How is an ammeter connected to the circuit?
A
It is always connected into the circuit
3
Q
How is the voltmeter connected to the circuit?
A
It is connected across a component in parallel
4
Q
What is the pd across all the cells equal to?
A
The sum of the pd’s across the bulbs in a series circuit
5
Q
The current is the same whenever..?
A
..you measure it in a series circuit
6
Q
What do more cells give the circuit?
A
- Bigger p.d
- Bigger current
- Brighter bulb
7
Q
What does more bulbs give the circuit?
A
- Lower current
- Dimmer bulbs
- Pd per bulb decreases
8
Q
What happens to all the bulbs in a series circuit if 1 goes out?
A
All the others also go out
9
Q
What happens to the bulbs in a parallel curcuit if one goes out?
A
They stay lit
10
Q
How many paths for the current in a seriews circuit?
A
Only 1
11
Q
How many paths for the current in a parellel circuit?
A
More than 1
12
Q
What is this?
A
A cell
13
Q
What is this?
A
A battery
14
Q
What is this?
A
An open switch
15
Q
What is this?
A
A closed switch
16
Q
What is this?
A
A filament lamp
17
Q
What is this?
A
An Ammeter
18
Q
What is this?
A
A Voltmeter
19
Q
What is this?
A
LDR (light-dependant resistor)
20
Q
What is this?
A
A diode
21
Q
Whats this?
A
An LED (light emitting diode)
22
Q
Whats this?
A
A fuse
23
Q
Whats this?
A
A resistor
24
Whats this?
A variable resistor
25
Whats this?
A thermister
26
What is the current?
The rate of flow of charge
27
What is the potential difference?
The pd between 2 points in an electric circuit is the work done (energy transferred) per coulomb of charge that passes between the points
28
Resistance
A measure of how hard it is for a current to pass through any component
29
What is the total resistance in a circuit?
R1+R2 (resistors added together)
30
What is the total pd in a circuit?
the pd's added together
31
When calculating the pd, if each cell =1.5V and the cells are facing the same way what is the total pd?
1.5+1.5 = 3V
32
When calculating the pd, if each cell =1.5V and the cells are facing opposite eachother what is the total pd?
1.5V-1.5V = 0V
33
Factors that effect resistance?
* Material
* Cross sectional area (thickness)
* Temperature
* Length
34
In terms of resistance - the longer the wire?
The more resistance
35
In terms of resistance - thinner wire =?
More resistant
36
In terms of resistance, the thicker the wire?
The lower the resistance
37
What does ohms law state?
The current through a fixed resistance will be proportional to the pd across the resistor providing the temoerature is constant
38
What is the equation for the resistace?
**R = I/V**
resistance = current / pd
39
Whats the equation for the gradient?
Rise
---------
step
40
What is the use of a diode?
Only allows current to flow thorugh in one direction so it can be used to protect electronic circuits
41
Whats the difference between a conducting and unconducting diode?
42
Use of an LDR
Can be used to **control circuits** as light sensors/automatically switches light etc because its **resistances changes **as the **light intensity changes **
43
Use of a thermistor?
In central heating systems as part of the thermostat of any circuit to **cont****rol temperature** because its resistance varies with temperature
44
Whats the use of LED's?
* In **small scale lighting** eg on electronic equipment
* In **low power lighting** in buildings
* **Brake lights ** because their long loved and very reliable
45
Static electricity: Two like charges..?
Repel
46
Static electricity: two unlike charges..?
Attract
47
Electrons (which are negative) can move from one \_\_\_\_?\_\_\_\_ to another due to ?
From one insulator to another due to rubbing/friction
48
What happens if something looses electrons?
It becomes positively charged
49
What happens if something gains electrons?
It will bcome negatively charged
50
What is the frequency and voltage of the mains electricity we use?
**Voltage** - 230V
**Frequency** - 50Hz
51
What is an alertnating current?
An electric current that continually changes its direction
52
Whats a direct current?
An electric current that flows in the same direction at all times
53
What is another source of electricity we use thats not mains?
Batteries, these have no frequency and have a direct current
54
What happens when a current passes through a resistor?
Heat energy is produced
(it can be good though eg kettle, iron)
55
How is a point of high resistance caused?
By damage in a wire, it can cause overheating
56
Why are ovens etc connected by thick wires?
So that the large current doesnt cause overheating
57
What happens when a large current pases through a thin fuse wire?
The wire melts and breaks the circuits
58
Whats the equations for normal current?
Power
\_\_\_\_\_\_\_\_\_
Voltage
59
Whats a RCCB and how does it work
**Residual current circuit breaker**
it works by comparing the current in the live and neutral wires if the icrrents are different they break the circuits up
60
What are the advantages of an RCCB?
**Resettable** (less mistakes made by changing fuses manually)
## Footnote
**Faster**
61
