Section 5 - Electricity and Circuits Flashcards
What is current?
The flow of electrical charge.
What is potential difference?
The driving force that pushes the charge around, the energy transferred per unit charge that passes between two points in a circuit.
What is resistance?
Anything that slows the current down.
What is the equation for charge?
Q=I×t
Q = Charge I = Current t = Time
What are some necessary circuit components?
Cell Battery Open switch Closed switch Filament lamp Fuse LED Power supply Resistor Variable resistor Ammeter Voltmeter Diode LDR Thermistor Motor Wire
Describe the equation relating potential difference, current and resistance.
V=I×R
V = Potential difference I = Current R = Resistance
Describe the normal trend between temperature and resistance.
As temperature increases, so does resistance.
What is an ammeter? How is it installed in a circuit?
It is a device that measures current, it must be installed in series as part of the main circuit.
What is a voltmeter? How is it installed in a circuit?
It is a device that measures potential difference, it must be installed in parallel to another circuit device.
What is a diode?
A device that only allows current to flow through it one way.
What is an LDR?
A device that changes its resistance in response to changes in light level.
What is a thermistor?
A device that changes its resistance in response to changes in temperature.
What is the trend between light and resistance in LDRs?
As light levels increase, resistance decreases.
What is the trend between temperature and resistance in thermistors?
As the temperature increases, resistance decreases.
What is a series circuit?
A circuit in which every device is connected to the next in one loop.
What is a parallel circuit?
A circuit in which devices may be connected to others in multiple loops. This makes the separate loops independent.
How does adding a resistor to a series circuit affect its total resistance?
It increases it.
How does adding a resistor to a parallel circuit affect its total resistance?
It decreases it.
Describe the equation relating energy transferred, voltage, current and time?
E=I×V×t
E = Energy transferred I = Current V = Voltage t = Time
What is the normal trend between current and temperature?
As the current increases, more energy is transferred to the thermal energy stores of the components, this increases temperature.
Describe the trend between heat and efficiency.
As heat increases, efficiency decreases.
What are some uses of heating in electronics?
Fuses, ovens, toasters, heaters and filament bulbs.
What is power?
A measure of how much energy is transferred per second.
What are the equations for power?
P=E/t
P=I×V or P=I²×R
P = Power E = Energy transferred t = Time V = Potential difference R = Resistance I = Current
What is a power rating?
How much energy is used by an appliance per second.
What type of current is mains supply?
A.C
What type of current is battery supply?
D.C
What does A.C stand for?
Alternating current.
What does D.C stand for?
Direct current.
What is the difference between A.C and D.C?
A.C is always changing direction where D.C can only go one way.
What wires do most cables have?
Live wire
Neutral wire
Earth wire
What is the live wire?
The red wire in a cable, it carries the current and has a voltage of 230 volts, this means touching it delivers an electric shock.
What is the neutral wire?
The blue wire in a cable, it completes the circuit and has a voltage of 0 volts, this means it doesn’t deliver electric shocks when touched.
What is the earth wire?
The yellow and green wire in a circuit, it is there for safety and prevents the casing of the appliance from becoming live, it has a voltage of 0 volts and does not deliver electric shocks.
What voltage is mains supply?
230 volts.
What are fuses?
Small insulated wires that are there to protect the circuit and appliance from any current surges.
How do fuses work?
Any abnormally large amount of current, a surge, will cause the fuse to melt and disconnect any power to the appliance, making it safe.
What is the trend between cable thickness and fuse rating?
As cable thickness increases, so does the fuse rating.
What are circuit breakers?
Switches that open, trip, under large currents, this prevents a surge.
What is double insulation?
Where the appliance has a plastic casing and no exposed metal.
