Electricity Flashcards
What is a switch?
used to turn a circuit on and off
What is a resistor
reduces the flow of a current
What is a fixed resistor?
a fixed resistor has a resistance that doesn’t change
What is a variable resistor?
adjusting this resistor changes its resistance
a variable resistor is used in some dimmer switches and volume controls
What is a thermistor?
the resistance of a thermistor depends on its temperature
at low temperatures the thermistor has a high resistance
as the temperature increases, the resistance increase
can be used in thermostats or heat activated fire alarms
What is an LDR? (Light Dependant Resistor)
the resistance of an LDR depends on light intensity
at low light levels the LDR has a high resistance
as the light intensity increases, the resistance decreases
can be used as a sensor in cameras or automatic lights
What is a diode?
allows a current to flow in one direction but not in the other
What is an ammeter?
measures the current (rate of flow of charge)
What is a voltmeter?
measures the potential difference (energy transferred per unit charge)
What is a current and what is it measured in?
the rate of flow of charge
Amps
What is the potential difference/voltage and what is it measured in?
the energy transferred per unit charge
volts
What is the rule for current in a series circuit?
the current stays the same everywhere in the circuit
What is the rule for current in a parallel circuit?
the current flows around the circuit from the power supply, then splits when it reaches a junction and rejoins at the second junction
What is the rule for potential difference in a series circuit?
What is the equation
The voltage of the power supply is split between the bulbs in the circuit
v1 = v2 + v3
What is the rule for potential difference in a parallel circuit?
the voltage of each bulb is the same as the power supply
v1 = v2 = v3
What is the rule for resistance in a series circuit?
the more resistors in the circuit, the higher the resistance
What is the rule for resistance in a parallel circuit?
the more resistors, the lower the resistance
Fill the gaps :
____ resistance will reduce the flow of current
___ resistance will allow a high current to flow
high resistance will reduce the flow of current
low resistance will allow a high current to flow
How is resistance caused? (three points)
- an electric current flows when electrons move through the conductor, such as a metal wire
- the moving electrons can collide with the ions in the metal
- this makes it more difficult for the current to flow, and causes resistance
What is resistance?
a measure of how much the electrical current is reduced by a component
What is resistance measures in?
Ohms (Ω)
How do you calculate the current?
What are the measurements used?
current = charge / time
Amps) (coulombs) (seconds
How do you calculate potential difference? (2 different calculations)
What are the measurements?
potential difference = energy / charge
(volts) (joules) (coulombs)
potential difference = current x resistance
(volts) (amps) (ohms)
What is charge measured in?
coulombs (C)
How do you calculate the resistance?
What are the measurements?
resistance = potential difference / current
(ohms) (volts) (amps)
Fill the gaps :
As the ______ of a wire increases, the resistance ________
As the __________ increases, the resistance ________
as the length of a wire increases, the resistance increases
as the temperature increases, the resistance increases
Why does the resistance increase if the temperature increases?
as the wire gets hotter, the particles gain more kinetic energy and vibrate more
this makes it harder for a current to flow through the wire, so the resistance will increase
What is ohms law?
for a conductor, . . .
for a conductor, the potential difference of the component will be directly proportional to the current flowing through it provided the temperature remains constant
