Do Now: Calculate the resistance of the conductor whose graph is given above.

Power & Energy in Electric Circuits Series Circuits

Power in Electric Circuits Rate at which energy is supplied to circuit P = VI

Example: Calculate the rate at which energy is supplied by a 120-volt source to a circuit if the current in the circuit is 5.5 amperes.

P = VI V I= R V2 P = R

Energy (W) E = VIt E = P t E=I2Rt V2t E = R

Example: How much energy is produced by a 50-volt source that generates a current of 5.0 amperes for 2.0 minutes?

Example: An immersion heater has a resistance of 5.0 ohms while drawing a current of 3.0 amperes. How much electrical energy is delivered to the heater during 200. seconds of operation?

An operating 100. -watt lamp is connected to a 120-volt outlet An operating 100.-watt lamp is connected to a 120-volt outlet. What is the total electrical energy used by the lamp in 60. seconds?

SERIES CIRCUIT Only ONE current path if that is interrupted, the entire circuit won’t work.

SERIES CIRCUIT Since only one path, current throughout the circuit is constant I = I1 = I2 = I3 = …

V = V1 + V2 + V3 +… SERIES CIRCUIT Potential difference (V) across 2 points depends on the work needed to get between those 2 points V drops across each resistor (not constant) V = V1 + V2 + V3 +…

SERIES CIRCUIT Ohm’s law holds for each resistance V = IR

Req = R1 + R2 + R3 + … SERIES CIRCUIT Req = equivalent resistance of the system Req = R1 + R2 + R3 + …

SERIES CIRCUIT We can find: Req = I = VR1= VR2= VR3=

SERIES CIRCUIT Req = 3 + 4 + 5 = 12 kΩ I = V/R = 1 mA VR1= IR1 = 3 V VR2= IR2 = 4 V VR3= IR3 = 5 V

Find: Req, I, VR1, VR2, VR3, VR4, VR5

Page 650: 1-6 Complete each problem AND draw the circuit described in each question (except #6, no drawing necessary)

EXIT QUIZ

1. What is the Req for this circuit? The accompanying circuit diagram represents four resistors connected to a 12-volt source. 1. What is the Req for this circuit? 2. What is the total current in the circuit? 3. What is the voltage across R1?