current ( i ) – the rate at which charge passes through a wire. units – c/s = amperes (a)
TRANSCRIPT
There is 3A of current moving through a point on a wire. How much charge passes that point in 30 seconds?
There is 3A of current moving through a point on a wire. How much charge passes that point in 30 seconds?
90C
2. Potential difference between two points in the circuit.
• May be supplied by a battery (has + and – terminals)
3. Conductive material through which charge can move.
• Metals are good conductors because their electrons move easily.
Resistance ( R ) – the opposition that a device or conductor presents to the flow of electric current.
Unit – Ohm (Ω)
Resistivity ( ρ ) – a measurement of how conductive a material is. (High resistivity means not as conductive)
Unit - Ω•m
ρLR=
A
A 6.5m long copper wire has a cross-sectional area of 3x10-3m2. What is the resistance in the wire?
R = 3.7x10-5Ω
A 0.686m long wire has a cross sectional area of 8.23x10-6m2 and a resistance of 0.125Ω. What is the wire made out of?
A 0.686m long wire has a cross sectional area of 8.23x10-6m2 and a resistance of 0.125Ω. What is the wire made out of?
Nichrome
Ohms’s Law – the ratio of the potential difference to the current is always a constant for a given conductor and is called resistance.
VR=
I
Resistor – a device used in a circuit to limit current flow or provide a potential drop.
Picture Symbol
Voltmeter – a device used to measure potential difference across a circuit.
Connect outside the direct path of the current (parallel connection)
Ammeter – a device used to measure the current through a circuit.
Connect in the direct path of the current (series connection)
Circuit Schematic – a diagram of an electric circuit using standard symbols for the circuit elements.
1. Begin by drawing the symbol for the battery or other source of electric energy (such as a cell or generator).
3. When the path of the current reaches a resistor or other device, draw the appropriate symbol with values.
Electrical Energy (W) – the energy made available by the flow of electrical charges through a conductor
Units – Joules (J)
22 V t
W = Pt=VIt=I Rt=R
QuantityQuantity SymbolSymbol UnitUnit FormulaFormula
Resistance
Voltage(Potential Difference)
Charge
Current
Power
Energy
Characteristics Series Circuit
Number of Paths
Current
Potential Difference (Voltage)
Total Resistance
Power
Disconnecting one bulb
Characteristics Parallel Circuit
Number of Paths
Current
Potential Difference (Voltage)
Total Resistance
Power
Disconnecting one bulb
Kirchoff’s Junction Rule - The total current directed into a junction must equal the total current directed out of the junction.
Junction D Junction E Junction F