 Ch. 34 Electric Current.

Presentation on theme: "Ch. 34 Electric Current."— Presentation transcript:

Ch. 34 Electric Current

Electric Current Movement or “flow” of charge
Occurs when there is a difference in voltage between the ends of a conductor Electrons carry charges through solid circuits

Electric Current (I) Current = charge I = q time t
Measured in amperes (amps or A) Example: Calculate the current where 20 coulombs of charge pass a point in 8 seconds.

Electric Current (I) Current = charge I = q time t
Measured in amperes (amps or A) Example: Calculate the current where 20 coulombs of charge pass a point in 8 seconds. 20 C / 8 s = 2.5 amps

Voltage Sources Provide a potential difference so that charges are able to flow Examples: Dry Cells or Wet Cells Energy from a chemical reaction is converted to electrical energy

Voltage (V) The potential energy per coulomb of charge available to electrons moving between terminals Typical voltage in a home is 120 V 120 Joules of energy are supplied to each coulomb of charge that flows in a circuit!!!

Charge flows because of an applied voltage across the circuit
Remember that…. Charge flows because of an applied voltage across the circuit

Electric Resistance (R)
Measured in ohms, Ω Depends on: Conductivity of material Diameter of wire Thick wires have less resistance than thin wires Length of wire Longer wires have more resistance than shorter wires

Ohm’s Law I = V/R Current = Voltage / Resistance
Units: amps = volts / ohms

I = V/R A 120 ohm heating element is powered by a 10 volt battery. What is the current?

I = V/R A 120 ohm heating element is powered by a 10 volt battery. What is the current? 10 V / 120 ohm = amps

Alternating Current (AC)
Direct Current (DC) Charge always flow in one direction Ex. Batteries Alternating Current (AC) Charge alternates directions as it flows Ex. Our outlets

Since our outlets produce AC current, but many appliances use DC, what can we do….. Convert AC to DC
Diode: a converter that only allows electrons to flow in one direction

Electric Power The rate at which electrical energy is converted into another form Power = current x voltage P = IV

Ch. 34 Practice

Ch. 35 Electric Circuits Series Circuits

For Problem Solving in Series
Resistances are ADDED R1 + R2 + R3 = R total

The resistance of one lamp is 10 ohms
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?

The resistance of one lamp is 10 ohms
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = = 30 ohms

The resistance of one lamp is 10 ohms
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = = 30 ohms If the attached voltage source is 10 V, what is the current in the circuit?

The resistance of one lamp is 10 ohms
The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = = 30 ohms If the attached voltage source is 10 V, what is the current in the circuit? I = V/R I = 10 V / 30 ohms I = 0.33 amps

Parallel Circuits = Rtotal R R R3

Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?

Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? 1/10 + 1/10 + 1/10 = 1 / Rtotal 0.3 = 1 / Rtotal Rtotal = 1/0.3 = 3.33

Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? Rtotal = 1/0.3 = 3.33 If the attached voltage source is 10 V, what is the current in the circuit?

Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? Rtotal = 1/0.3 = 3.33 If the attached voltage source is 10 V, what is the current in the circuit? I = V/R I = 10 V / 3.33 ohms I = 3 amps

Ch. 35 Lab and Practice