2.0 Energy Flashcards
1
Q
current
A
- the rate of flow of charge
- in a series circuit, the current is the same value at any point
- in a parallel circuit, current is shared between branches
2
Q
equation for current
A
current = charge/time I = Q/t
3
Q
What does mA mean
A
- milliamperes
- 10 mA = 10x 10^-3A
4
Q
Voltage
A
- driving force that pushes the charge around
- energy transferred per unit charge
- V
- in a series circuit the potential difference of the power supply is shared between the components
- in a parallel circuit the potential difference across each component is the same
5
Q
Resistance
A
- parts if the circuit that resists current flow
- Ω
- resistance of ohmic conductors (e.g. wire, resistor) doesn’t change with current
- resistance of components ( e.g. filament lamp, diode) does change
6
Q
Formula linking potential difference and resistance
A
- voltage = current x resistance
- V = IR
7
Q
I-V characteristic
A
- a graph which shows how the current flowing through components changes as the potential difference (voltage) across it is increased
8
Q
equation for power
A
- power = current x voltage
- p = I x V
9
Q
Advantages and disadvantages of series circuits
A
Advantages:
- all components can be controlled by a single switch
- fewer wires are required
Disadvantages:
- components cannot be controlled separately
- if one component breaks, they all stop working
10
Q
Advantages and disadvantages of parallel circuits
A
Advantages:
- components can be individually controlled
- if one component breaks, the rest continue to function
Disadvantages:
- many more wires are needed
- all components have the same voltage as the supply, so harder to control if components need to have different voltage
11
Q
relationship between energy transferred, current and voltage
A
- energy transferred = current x voltage x time
- E = I x V x t
12
Q
difference between alternating current and direct current
A
- alternating current means the current is constantly changing direction
- direct current is supplied by a cell or battery and flows in the same direction
13
Q
effect of changing resistance
A
- the higher the resistance of a circuit, the lower the current
- resistance of a circuit can be increased by adding resistors to it
14
Q
Light dependant resistors (LDRs)
A
- the resistance of an LDR changes depending on the light intensity of it
- as light intensity increases, resistance of the LDR decreases
- useful for burglar detectors, street lamps
15
Q
Light emitting diode (LED)
A
- they only allow current to pass in one direction through them and will only light if the current passes in that direction
- they can be used to indicate the presence of a current because they illuminate when current flows through them
16
Q
Thermistors
A
- resistance of a thermistor changes depending on its temperature
- as temperature increases, resistance decreases
- useful temperature detectors
- used to control a circuit
17
Q
fuses
A
- if the current becomes too large, the wire heats up and melts causing it to break and stopping the current
- makes sure that damage isn’t caused
18
Q
Alternating current
A
- a current that continuously changes direction, going back and forth around a circuit
- in UK mains electricity is an alternating current with a potential difference of around 230 volts
- alternating current transmits energy like a wave
19
Q
Direct current
A
- a current that is steady, constantly flowing in the same direction in a circuit, from positive to negative
20
Q
Difference between dc and ac
A
DIRECT CURRENT:
- stable voltage
- difficult to create high voltage
- difficult to change voltage
- produced by cells and batteries
- has a positive and negative terminal
ALTERNATING CURRENT:
- voltage fluctuates
- easy to create high voltage
- easy to change voltage
- produced by electrical generators
- has two identical terminals
21
Q
equation between energy transferred, charge and voltage
A
- energy transferred = charge x voltage
- E = Q x V
