physics topic two Flashcards
what is the function of a Switch (open)
Electricity can’t flow
what is the function of a Switch (closed)
Completes the circuit (lets electricity flow)
what is the function of a Cell
Provides PD and current for a circuit
what is the function of a battery
Provides PD and current for a circuit
what is the function of a lamp/bulb
Converts electrical energy to light energy
what is the function of a resistor
Slows down current and voltage
what is the function of a voltmeter
Measures PD – volts
what is the function of an Ammeter
Measure current – amps
what is the function of a fuse
Melts if current gets too high to stop electricity
what is the function of a diode
Forces current to only flow in one direction
what is the function of a Light Emitting Diode (LED)
Same as diode but gives off light
what is the function of a Variable Resistor
Can be used to change the resistance
what is the function of a Thermistor
The higher the temperature, the lower the resistance
what is the function of a Light Dependant Resistor (LDR)
The higher the light intensity, the lower the resistance
what is charge
Charge is the amount of electricity travelling through a circuit.
what is current and what is it measured in
a flow odd charged particals - measured in amps
what is voltage and what is it measured in
a measure of the difference in energy between one part of a circuit and another (How fast electrons move) - measured in volts
what is resistance and what is it measured in
the opposition to the flow of electric current in a material or circuit (Slows down current and voltage) - measured in ohms
what is potential difference
and what is it measured in
what does the resistance in a circuit depend on
The resistance in a circuit will depend on the components used in the circuit as
well as the length of wire used in the circuit. The longer the wire, the greater the
resistance.
what a a Circuit in series
Series circuits consist of one loop of wire.
give features For components connected in series
there is the same current through each component
the total potential difference of the power supply is shared between the components
the total resistance of two components is the sum of the resistance of each component.
what are Parallel Circuits
Parallel Circuits consist of two or
more loops (branches) of wire.
give features For components connected in parallel
the potential difference across
each component is the same
the total current through the
whole circuit is the sum of the
currents through the separate
components on each loop
(branch)
the total resistance of two
resistors is less than the
resistance of the smallest
individual resistor.
describe the IV Characteristics REQUIRED PRACTICAL
1) Measure the current in resistor using ammeter
2) Measure the p.d. across resistor using voltmeter
3) Vary the resistance of the variable resistor
4) Record a range of values of current and p.d.
5) Reverse connection of resistor to power supply
6) Repeat measurements of I and V in negative direction
7) Plot a graph of current against p.d.
what is ohms law
The resistor follows Ohm’s law (it’s an Ohmic conductor) and its resistance is constant.
Explain, in terms of the electrons and ions inside the filament, why both the temperature and the resistance increase
Ions in lamp/resistor vibrate faster
Electrons collide more with the ions
Increasing resistance and decreasing
current
what is something if its non-Ohmic.
it doesnt follow ohms law
what happens to to the resistance of LDR with increasing light intensity
resistance decreases
describe Circuit resistance REQUIRED PRACTICAL
1) Have 3 lengths of wire (10cm, 20cm, 40cm) measured with a ruler
2) Measure current and potential difference using an ammeter and voltmeter
3) Take repeat readings and calculate a mean
4) Switch off circuit in between each reading to allow wire to cool
5) Calculate resistance by using: r = v / i
6) Plot a graph of resistance against length
what is direct current
Direct current moves in one direction only
what is alternating current
Alternating Current repeatedly reverses direction
what is The UK mains supply
The UK mains supply is 230 V. and has a frequency
of 50 Hz (50 hertz)
what are the components of a plug
Live wire (brown) – Carries
current and voltage (230V)
Neutral wire (blue) –
Completes the circuit (0V)
Earth wire (green + yellow
stripes) – Earths appliance
Fuse – Wire inside melts if
current gets too high
what is the purpose of earthing appliances
if live wire touches case
current flows to earth
how are plugs double insulated
case is made of insulator (plastic)
cable is (also) insulated
what is the National grid
A series of transformers, power cables and pylons
what are step-up transformers
Increases potential difference
Decreases current
Reducing thermal energy transfer to surroundings from transmission cables
Increasing efficiency
what are step-down transformers
Decreases potential difference
To a safe value
what are static charges
These are positive (+) and negative (-) charges.
When two electrical charges interact, they produce Electrostatic forces - non contact forces
how does Charging by friction work
When two objects are rubbed together (friction), electrons transfer from one to the other.
One object will become positive and the other will become negative
what is An electric field the region
the region (around a charged object) where
another charged object experiences a force
