Electricity Flashcards
From which end of a cell does the electric current flow from and to?
From the POSITIVE end of the cell TO the NEGATIVE end (known as conventional current).
What is a series circuit?
A circuit that has NO BRANCHES and the CURRENT can only flow in ONE PATH.
What is key about current in series circuit?
The CURRENT is the SAME all the way around a series circuit.
What is key about current in parallel circuits?
The CURRENT in the branches ADDS UP to the TOTAL CURRENT leaving the cell.
What is meant by potential difference (voltage)?
A potential difference of 1 volt tells us that 1 JOULE of energy is TRANSFERRED for EACH COULOMB OF CHARGE that is moving through the circuit.
What is key about potential difference in parallel circuits?
The potential difference across each COMPONENT is the SAME.
What is key about potential difference in series circuits?
What equation do you use to calculate charge flow?
charge flow (C) = current x time Q = I x t
What equation do you use to calculate energy transfer?
energy transferred = charge flow x potential difference E = QV
What is meant by resistance in circuits?
Tells us the potential difference required to drive a current through a component.
aWhat equation do you use to calculate resistance?
resistance (Ω) = potential difference / current R = V / I
What can we say about current through a resistor to potential difference?
Current through a resistor is DIRECTLY PROPORTIONAL to the potential difference.(Resistor is an example of an OHMIC CONDUCTOR).
What key factor ensures that current through a resistor is directly proportional to the potential difference.
If the TEMPERATURE is constant.
How can resistors be useful in circuits?
Can be used to SHARE potential difference allowing for light for example to be DIMMER as less electrical energy is transferred to the lamp.
What can we say about current through a filament lamp to potential difference?
The current through a filament lamp is NOT directly proportional to potential difference. (Filament lamp is an example of a NON-OHMIC CONDUCTOR).
Why is the current through a filament lamp not directly proportional to the potential difference?
This is because the filament gets HOT so the RESISTANCE INCREASES.
What is key about current in diodes?
The current flows in ONE DIRECTION only.
What can we say about current through a diode to potential difference?
Why can the current only flow through one direction in a diode?
As it has a very high resistance in the reverse direction.
Why are diodes useful?
For controlling the flow of current in circuits.
What can we say about resistors in series circuits?
The resistors ADD together.
What can we say about resistors in parallel circuits?
The TOTAL RESISTANCE of two resistors is LESS than the resistance of the SMALLEST individual resistor.
Label the live, neutral and earth wire on plug:
What is the current in UK mains electricity?
Alternating current (AC). The current is constantly changing dicrection.
What is the main benefit of using AC?
It is very easy to use a transformer to increase or decrease the potential difference.
What is the frequency and potential difference of alternating current in the UK?
50Hz and 230v
How can scientists see the pattern of an electrical current?
Using an oscilloscope
What does a AC graph look like?
What does DC graph look like?s
How would you calculate the frequency of this wave?
