1. Cells have positive and negative electrodes.
Electrons build up on the negative electrode.
Current is the amount of e- moving – coulomb
Current is measured in Amperes.
Voltage is the difference between the potential
energy of electrons at two point in a circuit.

2. 5.5 Volt battery 0 Volts 5.5 Volts + electrode - electrode
electrolyte paste
5.5 Volts

3. Circuits can either be opened or closed by a switch. e-● + - ● + - e-
Open circuit (off)
Closed circuit (on)

4. Resistors, loads
and
Ohm’s Law

5. Electrons lose energy as they move through things.
Resistor: electrical device in a circuit that takes potential energy from electrons – resistance.
Electrical symbol – R
Unit is the ohm (Ω)
The loss of potential energy over a resistor is called the “voltage drop”
Schematic Symbol

6. Resistors are sometimes used to reduce the energy of a circuit for safety reasons.
Any resistor that takes the energy and converts for use – load.
Mechanical Energy
Thermal Energy

7. e- + - e- Load a resistor that converts energy. Resistor lowers energy● + -
Load
a resistor that
converts energy. e-
Resistor
lowers energy
removed as heat

8. Ohm’s Law - The voltage in a wire is equal to current multiplied by resistance.

9. A bulb that has 2. 4 A flowing through it, has a resistance of 16 Ω
A bulb that has 2.4 A flowing through it, has a resistance of 16 Ω. Calculate the voltage drop across the load – energy lost by the electrons to light up the bulb. e- ● + -
V =
I · R
38.4 V
= (2.4 A) · (16 Ω)
= 38.4 V e-

10. A 9 V battery is hooked up to a metal wire to make a circuit
A 9 V battery is hooked up to a metal wire to make a circuit. If the metal wire has a resistance of 6.5 Ω, calculate the current in the wire. e- V R
I = ● + -
9 V
6.5 Ω = e-
= 1.38 A

11. V I R Voltage – Energy lost by the electrons through the circuit.
Current – Number of electrons moving through the circuit.
Resistance – the ability of a load or resistor to take energy.
I R V