Electricity Flashcards
A circuit diagram shows how ____ are connected together
Components
For components in series, the potential differences ____ to give the total potential difference.
Add up
The resistance of a filament lamp ____ with increase of the filament texture.
Increases
Resistance (Ohms) =
Potential difference (Volts)
Resistance (Ohms) = —————————-
Current (Amps)
The current through a resistor at constant temperature is directly _____ to the potential difference across the resistor.
Directly proportional
For components in parallel, the potential difference is ____ in each component.
The same
A ____ consists of two or more cells connected together.
A battery
For components in series, the resistances ____ to give the total resistance.
Add up
For a diode, its ‘forward’ resistance is ____ and its ‘reverse’ resistance is ____.
Forward resistance s low and reverse resistance is high
For components in parallel, the total current is the ____ of the currents through each component.
Total
The resistance of a thermistor decreases if its temperature ____.
Increases
For components in parallel, the bigger the resistance of a component, the ____ the current is.
Smaller
Charge (Coulombs) =
Charge (Coulombs) = Current (A) x Time (s)
Where would you get a direct current?
From a cell or battery
List good electrical conductors
Silver, Copper, Graphite, Other metals etc
Describe lightning in terms of the movement of electrons
A charge builds up in water droplets in a cloud due to friction. This can induce an opposite charge in tall objects, leading to electrostatic attraction. The electrons are attracted and ‘jump’ as an electrostatic discharge.
What are the units for the equation, Power = Current x Voltage
Watts = Amps x Volts
List some common insulating materials
Glass, plastic, wood, rubber, fabric etc
Energy transferred=
Energy transferred (J)= Current (A) x Voltage (V) x Time (seconds)
List and describe some danger of electrostatic charges
Fuelling aircraft or tankers: A build up of too many electrons can discharge as a spark, causing a fire or explosion.
Which appliance allows current to flow more when the temperature increases?
Thermistor
Energy transferred (J) =
Energy transferred (J) = Power (Watts) x Time (s)
Why is a parallel circuit more suitable for domestic lighting? Give two reasons.
- The lights can be switched on/off independently
- Any broken bulb will not effect the whole circuit.
Electrical power supplied (Watts)=
Electrical power supplied (Watts)= Current (A) x Potential difference (V)
Why does a rubbed balloon make your hair stick up?
The rubbing causes a movement of electrons, leaving a static charge. This charge induces the opposite charge in the hair, causing an electrostatic attraction.
What is the difference between electricity and electrostatics?
Electricity: In conducting materials, electrons flow when given energy by a power supply.
Electrostatics: In insulating materials, electrons moved by friction, charge builds up
An electric current is a flow of ____
Electrons/ Negative charge
What are the properties of mains current?
- Alternating Current
- 50Hz
- 230V
What type of material can be charged by friction?
Insulating materials
List and describe some uses of electrostatics
Laser copier/ printer: The image is ‘drawn’ by laser leaving a charge. The ink particles are given the opposite charge and stick to the place, then heated on.
Inkjet printer/ paint gun/ crop sprayer: Particles are given a charge so that they repel each other and give an even coverage without clumping
What types of material does static electricity build up in?
Any insulator
Is the current and the potential difference the same all the way around a series circuit?
Yes, the current is the same but the voltage is not
The power supplied to a device is the energy transfer to it every ____.
Second
If you increase the resistance of a circuit, what happens to the current?
Decreases, V=IR
What is an electrostatic charge?
When friction causes a transfer of electrons. This creates a negative charge where they build up, and a positive charge where they were moved from.
Describe some safety features of electrical devices
Fuses, circuit breakers, earthing, insulating materials etc
What is the power of a mains lamp that needs 5 amps to run it?
Power = Current x Voltage Power = 5 x 230 Power = 1150W
When charge flows through a resistor, electrical energy is transferred as ____
Heat or thermal energy
What affects the size of the current in a series circuit?
The voltage, and the number and the resistance of the components in the circuit.
When an insulating material is rubbed, what particles move?
Electrons
List some hazards of using electricity
- Frayed cables
- Long cables cause a trip hazard
- Water around sockets
- Fingers/ objects pushed into plugs
- Electrocution
Sockets, plugs, wire casing and some electrical devices are made of ____ materials for safety reasons.
Insulating
What is voltage?
The energy transferred per unit of charge passed, ie a Joule per Coulomb
Opposite charges ____
Attract
What fuse should I choose if I want to light a 60W bulb in a 19V circuit? 1A 3A 5A 13A
5 amps
A fuse contains a thin wire that heats up, melts and breaks the circuit if ____ current passes through it.
Too much, or more current than the fuses value
Current is
The rate of flow of negative charge
Like charges
Repel
Which fuse should I choose if I want to light a 40W bulb in a 4V circuit? 1A 3A 5A 13A
13A
The resistance of an LDR ____ if the light intensity on it increases.
Decreases
Mains electricity is an alternating current supply. Alternating current repeatedly _____ its direction
Reverses
For components in series, the current is ____ in each component.
The same
Cables consist of two or three insulated wires made of ____
Copper
How many blondes does it take to change a lightbulb?
None
