Electricity Flashcards
how are electric circuits shown as diagrams
with circuit symbols and straight lines, components shouldn’t be on corners
what is the difference between a battery and a cell
a cell is one and a battery is multiple
what determines the size of an electrical current
the voltage of the battery and the resistance of the components
what’s the equation including current, charge & time
current = charge / time
what is potential difference
a measure of the work done or energy transferred to the lamp by each coulomb of charge that passes through it. The unit of potential difference is the volt (V).
what is resistance and what is its unit
a way of saying how difficult it is for electricity to flow through and is measured in ohms Ω
what is ohms law
Ohm’s Law is a formula used to calculate the relationship between voltage, current and resistance in an electrical circuit.
what happens when you reverse the potential difference across a resistor
it would flow in the opposite direction creating a negative reading
what happens to the resistance of a filament lamp as its temperature increases
it increases due to energy being given off through heat
how does the current through a diode depends on the potential difference across it
when the potential difference gets low enough all of the reading of current become 0
what happens to the resistance of a temperature-dependent resistor as its temperature increases
When temperature increases, the resistance increases
what happens to the resistance of a light-dependent resistor as the light level increases
resistance decreases as the light intensity increases
Describe the current, potential difference, and resistance for each component in a series circuit
the current is the same at each resistor, the individual potential differences added together, circuit is equal to the sum of individual resistances
Describe the potential difference of several cells in series
the total equals the voltage of the power supply
how to calculate the total resistance of two resistors in series
Rtotal = R1 + R2 +R3
why does adding resistors in series increases the total resistance
increases as more components are added
describe the currents and potential differences for components in a parallel circuit
charge divides up into separate branches, circuit is equal to the potential difference of just one of the cells
Calculate the current through a resistor in a parallel circuit
I = ΔV / R
Explain why the total resistance of two resistors in parallel is less than the resistance of the smaller individual resistor
more current flows from the source than would flow for any of them individually
Explain why adding resistors in parallel decreases the total resistance
because there are more paths for the current to pass through
which equation includes potential difference, energy transferred & charge
potential difference across a component (V) = energy transferred (E) (joules, J)/ charge (Q) (coulombs, C)
which equation includes resistance, potential difference, current
resistance (R) (ohms, Ω) = potential difference (V) (volts, V) / current (I) (coulombs, C)
what is direct current and what is alternating current
a direct current is an electric current flowing in one direction only, an alternating current is the flow of electric charge that periodically reverses
what is meant by the live wire and the neutral wire of a mains circuit
The wire covered in brown plastic is the live wire. This carries the 230 V alternating potential difference from the power supply. The wire covered in blue plastic is the neutral wire and this completes the circuit from the appliance back to the supply. It is usually at 0 V
Describe the National Grid
the network of power stations, powerlines and electricity infrastructure that allows electricity to be generated, transported and used across the country
what is the casing of a mains plug or socket made of and explain why
they have plastic casings, or they have been designed so that the live wire cannot touch the casing
what is in a mains cable
A plug connects a device to the mains electricity supply
what are the colours of the live, neutral, and earth wires
Live Brown
Neutral Blue
Earth Yellow and Green
why does a three-pin plug include an earth pin
it provides a path for current to flow from the case of the device to the ground if there is a fault
how are power and energy related
Energy is the ability to cause change; power is the rate energy is moved, or used.
calculate the energy transferred in a given time
Energy transferred = power x time
equation including power, current and potential difference
power supplied (P) (watts, W) = current (I) (amperes, A) x potential difference (V) (volts, V)
equation using charge, current and time
Current = charge / time
what are the energy transfers when electric charge flows through a resistor
transferred as heat
equation including energy transferred, charge and potential difference.
energy transferred = charge x potential difference
equation using power, current and potential difference
power supplied (P) (watts, W) = current (I) (amperes, A) x potential difference (V) (volts, V)
equation using power, energy transferred and time
Power (P) (watts, W) = energy transferred (E) (joules, J) / time (t) (seconds, s)
equation using power, current and resistance
power (P) (watts, W) = current squared (amperes, A) x resistance (R) (ohms, Ώ)
equation including charge, current and time
charge flow (Q) (coulombs, C) = current (I) (amperes, A) x time taken (t) (seconds, s)
what is a current
stream of charged particles, such as electrons or ions, moving through an electrical conductor or space
current equation
current = charge x time
how does the resistance of a thermistor change depending on temperate and light intensity?
temperature : decreases as temp increases
light intensity: decreases as light increases
how does the resistance of a LDR change depending on temperate and light intensity?
temperature: decreases as temp increases
light intensity: decreases as light increases
what are the uses of LDRs and thermistors?
LDRs : detect light levels e.g. automatic security lights
Thermistors: ovens and refrigerators
what is the purpose of transformers in the national grid?
lower the voltage and bring it down to a usable level
what is the equation involving potential difference and coil?
potential difference across primary coil x current in primary coil = potential difference across secondary coil x current in secondary coil
what happens when insulating materials are rubbed against eachother?
they become electrically charged
what happens when 2 electrically charged objects are brought close together?
they exert a force on each other. Two charged objects may either pull towards each other (attract) or push each other away (repel).
describe an electric field
positive to negative
