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
P=
2
V
R
V
I= R
Energy (W)
E = VIt
2
E=I Rt
E=Pt
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. 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 = …
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
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
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?