Topic 2 - Electricity - 2.1 Current, Potential Difference and Resistance Flashcards
Draw the circuit symbol for a cell.
Draw the circuit symbol for a battery.
Draw the circuit symbol for a lamp.
Draw the circuit symbol for a fuse.
Draw the circuit symbol for a voltmeter.
Draw the circuit symbol for an ammeter.
Draw the circuit symbol for a diode.
Draw the circuit symbol for a resistor.
Draw the circuit symbol for a thermistor.
Draw the circuit symbol for a variable
resistor.
Draw the circuit symbol for an LDR.
Draw the circuit symbol for an LED.
What is electric current?
The flow of electrical charge.
State the equation linking charge, current
and time. Give the units for the quantities
involved.
Q = I t
Charge (Coulombs), Current (Amperes),
Time (Seconds)
What can be said about the value of
current at any point in a single closed
loop?
Current is the same at all points in a
closed loop.
What two factors does the current in a
circuit depend on?
- Potential Difference (V)
- Resistance (R)
What equation should be used to
calculate potential difference if current
and resistance are known? State the
units for all 3 quantities.
V = I R
Potential Difference (V), Current (A),
Resistance (Ω)
What is an ‘Ohmic Conductor’? State the
condition required.
●A conductor for which current and potential
difference are directly proportional
●Resistance remains constant as current
changes
●Temperature must be constant
List four components for which
resistance is not constant as current
changes.
- Lamps
- Diodes
- Thermistors
- Light Dependant Resistors (LDRs)
What happens to the resistance of a
filament lamp as the temperature
increases? Why?
●Resistance increases
● Ions in metal have more energy, so vibrate
more, causing more collisions with
electrons as they flow through the metal,
creating greater resistance to current flow
What is different about current flow
through a diode?
●The current only flows in one direction
●Resistance is very high in the other
direction, preventing current flow
State what happens to the resistance of
a thermistor as temperature increases.
The thermistor’s resistance decreases.
Give two examples of when a thermistor
may be used.
- In a thermostat to turn a heater on
below a certain temperature - In a freezer to turn on a cooler when
the temperature becomes too high
State what happens to the resistance of
a LDR as light intensity decreases.
The LDR’s resistance increases.
Give an application for a LDR.
●Street lights often use LDRs
●When light levels become too low, the
light gains sufficient current to turn on
