Phys 9: Electric Current

Current electricity

Flow of electric charge (electrons)

Electric circuit

Continuous path for electricity to flow through

Parts of Electric Circuit: Energy Source (2)

• Joule (J) = measuring energy, provided by electrons

• Quantity of energy that is available from each electron is “electric potential” of electron

Sources (5)

• Electric cell - Converts chemical energy to electrical energy (through chemical reactions); contains electrolyte & +/- electrodes

• Primary cell: Unable to recharge, chemical reactions are irreversible

• Secondary cell: Able to recharge with electric energy to reverse chemical reaction

• 2 or more electrochemical cells = “Battery”

• Example: power lines, generating stations

Loads (3)

• Device that converts electric energy into other form of energy

• Example: light bulbs, heater, phones, toys

• Convert → forms of different energy: light, heat, sound

Law of Electric Charge: Pathways (2)

• Conducting wires that connect energy source to load = creates a controlled path where electric charge flows

• Example of Common Metal Used: Copper

Series in circuit

One path for electricity to flow through

Parallel in circuit

2 or more paths of electricity to flow through

Electric current (2)

• Flow of electrons. Amount of electric charge that passes a point in a given interval (time)

• Unit: Amperes (A)

Equation to calculate current & what each variable means + units?

• I = Q/t

• I = current, Q = quantity of electric charge (coulombs, C), t = time (s)

Steps to measure electric current (4)

• Measured with ammeter - device which measure amount of electric current at a point in circuit

• Connected directly in path of moving electric charges

• Connected in series in circuit

• Measure in amperes (A) or milliamperes (mA)

Conventional current (not real - was thought was true)

Protons were though to move/flow

Electron flow (“true flow”)

Electrons move/flow in current

Types of Current: Direct Current + example

• Electric current flows in single direction

• Example: Battery operated devices

Types of Current: Alternating Current + examples (2)

• Electrons periodically reverse direction (60 times/s in AC circuits in North American)

• Examples: Power lines, plugs, hydroelectricity