Methods of Charging Conduction – A Charged Object comes in CONtact with a neutral object. – The neutral object takes on the same Net Charge as the Charged Object Induction – A Charged Object is near a neutral object, – A third party (human finger) takes or gives Negatives to the neutral object. – That neutral object takes on the opposite Net Charge The whole system is grounded (neutralized)

Coulomb’s Law F = F = electric force, in Newtons k = constant = 9.0 x 10 9 Q = charge on one object, in Coulombs d = distance of separation between 2 objects, in meters q = charge on other object, in C

Now do the same for a negative charge!

Electrical Potential = PE/Q Think in terms of Plumbing and water flow Electrons - Positive Terminal Negative Terminal Chemical Energy 7

Electric Current A battery cell and a turning motor do the same thing: give negative charges- electrons- energy by separating them from the positives The electric potential- Voltage- of the whole system is the ratio of the total energy to the total charge. The “Voltage” rating of the battery is the difference in electric potentials of the positives & the negatives Voltage- “pushes” electrons through wires – Symbol: V – Units: volts (V)

Simple Circuit Connections V IR Ohm’s Law I = units: R = units: Current! Amperes Resistance Ohms

Arranged Sequentially Arranged Sequentially V battery =V 1 + V 2 + V 3 +… V battery =V 1 + V 2 + V 3 +… R eq = R 1 + R 2 + R 3 + … R eq = R 1 + R 2 + R 3 + … I battery = I 1 = I 2 = I 3 I battery = I 1 = I 2 = I 3 – = V battery / R eq As # of resistors increases in series, current decreases As # of resistors increases in series, current decreases Current is impeded by more & more resistors Current is impeded by more & more resistors Series Circuits

Parallel Circuits  All get the same Voltage (same as battery) V TOT =V 1 =V 2 =V 3 =…  Arranged Simultaneously  As # of resistors increases in parallel, current increases  Current is given more options, so it is allowed to increase

Analogy

Looking at Circuits…

Power Power is the rate at which electrical energy is supplied to a circuit or consumed by a load. Units: Watts (W)

Other Power Equations P=IV V=IR So… P=I 2 R