Physics: Mid-unit test
Electrical charge carriers
Equations/Relationships
Potential difference (voltage)
Resistance
Series Circuits: RTotal = R1+R2+R3
Parallel circuits: 1/RTotal = 1/R1+1/R2+1/R3
Voltage
Series circuits: Vs = V1+V2+V3
Current
Parallel Circuits: Vs = V1 = V2 = V3
Series circuits: Is = I1 = I2= I3
Parallel circuits: Ip = I1 + I2 + I3
Ohm's Law
V=IR
V1/V2 = R1/R2
V1 = (R/1)/(R1 + R2)Vs
Current: Energy transferred per unit time
Charge, current & time
Q=It
Q = It
Alternating current: Does not have a positive of negative terminal, but the direction of the current changes
Direct current: Flows from positive to negative. Supplied by batteries and lab power supplies
Wavy line on oscilliscope trace
Peak voltage is not the rated (real) voltage
Straight line on oscilloscope trace
A charged particle experiences a force in an electric field
Two negative charges will repel
A positive charge and a negative charge will attract
the path a charged particle follows:
Between two oppositely charged parallel plates
Near a single point charge
Between two oppositely charged points
Between two like charged points
Potential difference IS voltage
LURD: Light Up Resistance Down
TURD: Temperature Up Resistance Down
As resistance changes the share of the voltage each component takes also changes
To calculate the gradient of a line on a graph: y1 - y2/x1-x2
Circuit Symbols
Cell: Provides voltage
Battery: Provides voltage
Lamp: Produces light
Switch: controls current (on/off)
Resistor: Controls resistance (fixed)
Variable resistor: Controls resistance
Voltmeter: Calculates voltage
Ammeter: Calculates current
LED: Produces light
Motor: Converts electrical energy to kinetic energy
Microphone: Converts sound energy to electrical energy
Loudspeaker: Converts electrical energy to sound energy
Fuse: Limiting current
Photovoltaic cell: Converts light energy to electrical energy
Diode: Controls current direction
Capacitor: Storing charge
Thermistor: Detecting temperature changes
LDR: Detecting light changes
Relay: Circuit connecting switch
Transistor: Controllable switch