Physics Test - Current, Resistance, Ohm's Law, Power, Energy, Series & Parallel Circuits
Requirements for a Continuous Circuit
1. Closed Path 2. Energy Source (EMF) 3. Charges
Resistance in a Series Circuit
SUM Total R = R₁ + R₂ + R₃
Voltage in a Series Circuit
SUM Total V = V₁ + V₂ + V₃
Parallel Circuit
A circuit in which every resistor has its own connection to the power source
Simple Circuit
A circuit with one resistor
Series Circuit
A circuit with only one path for charges to move through
Ammeter
A device that counts the number of electrons and determines current that must be connected INSIDE the circuit
Voltmeter
A device that detects energy/charge and determines potential difference (voltage) that must be connected PARALLEL to the circuit
Electric Meter
A device that measures energy
Shunt
A device with low resistance
Crossing a Battery, Negative to Positive
ADD Battery's Voltage
Negative
Black
Kirchhoff's Junction Rule
Conservation of Charge: The sum of the currents entering (directed into) a junction is equal to the sum of the currents leaving (directed out) a junction
Kirchhoff's Second (Loop) Rule
Conservation of Energy: The algebraic sum of the voltage drops/gains around a closed circuit is always equal to 0
Current and Voltage Relationship
Direct
Electrical Energy Formulas
E = Pt = IVt = I²Rt = (V²t)/R
Current in a Series Circuit
EQUAL Total I = I₁ =I₂ = I₃
Voltage in a Parallel Circuit
EQUAL Total V = V₁ = V₂ = V₃
Crossing a Resistor, Opposite Direction as Current
Energy Gain: ADD Resistor's Voltage
Crossing a Resistor, Same Direction as Current
Energy Loss: SUBTRACT Resistor's Voltage
Conventional Flow
Flows from POSITIVE to NEGATIVE
Current and Resistance Relationship
Inverse
What happens to the overall resistance of a circuit when more resistors are added in series?
It becomes GREATER
What happens to the overall resistance of a circuit when more resistors are added in parallel?
It becomes LESS
Resistance Unit
Ohms
Electrical Power Formulas
P = (Q · v) / t
Resistance in a Parallel Circuit
RECIPROCAL SUM Reciprocal of Total R = 1/R₁ + 1/R₂ + 1/R₃
Positive
Red
Crossing a Battery, Positive to Negative
SUBTRACT Battery's Voltage
Current in a Parallel Circuit
SUM Total I = I₁ + I₂ + I₃
Current (I)
The rate at which charge flows, in amperes (amps)
Ohm's Law
V = IR
Unit of Power for a Small Object (i.e. Lightbulb)
Watt
Factors Affecting Resistance
1. Length 2. Cross-Sectional Area 3. Material
Unit of Power for a Medium Object (i.e. School)
Kilowatt (10³)
Unit of Power for a Large Object (i.e. Town)
Megawatt (10⁶)
Electron Flow
NEGATIVE to POSITIVE
What happens if you hook up the voltmeter/ammeter backwards?
They will give a negative reading.
EMF
This does NOT supply electrons, it merely gives them energy ("Electron Pusher")
