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ELECTRICITY-CIRCUITS
Joe Walker
Ryan Loyland
Ozan Berlinguette
ELECTRICITY VOCABULARY
Electricity = Caused by the flow of electrons
Positive charge = lacking electrons
Negative charge = excess of electrons
Ion = An atom that has a different amount of electrons than what is normal
Insulator = A material that resists electrical flow (Rubber)
Conductor = A material that does not have a high resistance (Copper)
CONCEPTS
• Electricity flows from negative charge to positive charge
• Any path for electrons to flow is a circuit
• An open circuit will not have any electrical flow
• The flow of charge in a circuit is very much like the flow of water in a
closed circuit
• Neither water nor the electrons concentrate in certain places.
• They flow in a continuous loop, or circuit.
CIRCUITS VOCABULARY
Wire = Allows electricity to flow in a circuit
Battery = Pushes electricity threw the circuit
Switch = can stop or control the flow of electricity
Resistor = provides resistance to the circuit
Fuse = Prevents too much current from passing through the circuit
Junction = where branches of the circuit join or split
EQUATIONS
I = V/R
I = Current in amperes V = Volts R = Resistance in ohms
W=VI
W=Watts=Power
Series circuit:
R(total) = R1+R2+…
Parallel circuit:
1/R(total)= 1/R1+1/R2+…
SERIES CIRCUIT
• No Branches
• Current is calculated by:
V/Total Resistance
• Total Resistance is the sum of
resistances
• When one part of he circuit is
open, the whole circuit will break
PARALLEL CIRCUIT
• Each device operates independent
of the other devices.
• A break in any of the paths does
not interrupt the flow of the
other paths.
• Voltage is the same across each
device
• The total current is divided
among the separate branches.
• The total current is the sum of
the currents in its branches.
SAMPLE PROBLEM
Two identical resistors, each with a resistance of 1500 ohms, are wired in
series with a 9 volt battery. (A) Find the current through each resistor (B) find
the voltage difference across each resistor.
(A) C= V/R C=9V/3000 ohms C= .3mA
(B) Product/Sum = (9V * 9V)/ (9V + 9V)=4.5V
EXAMPLES OF CIRCUITS
Simple Circuit
Parallel Circuit
COMBINATIONS OF RESISTORS
series
parallel
Current through
same
add
Voltage across
add
same
resistance
R(total)= R1+R2…
1/Rtotal=1/R1+1/R2…
CIRCUIT SAMPLE PROBLEM
You have an 800W microwave oven, a 450W toaster, and a 650W blender all
plugged into the same 110V household circuit, which has a 15A circuit breaker
installed. Can you turn on all three devices at the same time without tripping
the breaker?
Answer: No, the require 17.3 A
MULTIPLE CHOICE!
1. Any path along which electrons can flow is a(n)__________?
A. Current
B. Electron path
C. Circuit
D. Resistor
2. When connected in a _____, the devices in a circuit form (a) _______, for
electron flow.
A. series, single pathway
B. series, branches
C. parallel, single pathway
D. parallel, no pathway
3. If one device fails in a series circuit, current in the whole circuit stops and
none of the devices will work.
A. True
B. False
4. Which is not a characteristic of parallel connections?
A. The total current divides among the parallel branches.
B. The total amount of current in each branch is inversely proportional to the
resistance of the branch.
C. The total current is the sum of the currents in the branches.
D. The total current is the product of the currents in its branches.
5. The equivalent resistances of three 4 ohm resistors in series is?
A. 11 ohms
B. 12 ohms
C. 10 ohms
D. 7 ohms
6. Does current flow through a resistor or across a resistor?
A. Through
B. Across
7. Is voltage established through a resistor or across a resistor?
A. Through
B. Across
8. A 200 ohm resistor is connected to a 6-V battery. How much current flows
through the resistor?
A. 0.03 A
B. 1200 A
C. 0.012 A
D. 40 A
9. A 100 ohm resistor and a 500 ohm resistor are wired in series with a 15-V
battery. How much current flows from the battery?
A. 0.020 A
B. 0.025 A
C. 60 A
D. 0.15 A
10. A light bulb has a resistance of 300 ohms and a current of 0.20 A flows
through the bulb. What is the voltage difference across the bulb?
A. 60 V
B. 20 V
C. 70 V
D. 30 V
MC ANSWERS
1. C.
2. A.
3. A.
4. D.
5. B.
6. A.
7. B.
8. A.
9. B.
10. A.