The three main quantities in any circuit are voltage, current, and resistance. Voltage is the potential energy that pushes electrons through the circuit and is measured in volts. Current is the flow of electricity through a circuit and is measured in amps. Resistance is a material's ability to resist or allow the flow of electric current and is measured in ohms. A change in one quantity causes changes in the other two based on Ohm's Law.

1. Quantities of a Circuit

2. The 3 Quantities of a Circuit
• In any circuit, Voltage, Current, and
Resistance are all interconnected
– Change one, change them all

3. Ohm’s Law
Voltage
Current
I=V (volts)
(amps)
R Resistance
(ohms)
• As voltage increases, so does the current
• If resistance increases, the current decreases

4. Voltage
• Related to potential energy (stored energy)
– Differences in electrical energy pushes electrons
through circuit
– We measure it in volts
• Ex) Batteries

5. How Batteries Work
• Inside battery are chemicals that separate (+)
& (-) charges
• When wires are connected, the charge flows
from (+) to (-) and neutralize battery
• Most batteries are 1.5 V batteries
– The positive end of a battery is 1.5 V higher than
the negative end

6. Types of Batteries
• D-cell, AA, AAA
– Lettered batteries (AAA, AA, C, D) have the same
volts (1.5 V)
– Difference is in how long they’ll last
– Bigger they are (D), the longer they’ll last
• Batteries can be paired together to create a
higher voltage

7. Current
• Amount of electricity flowing
• More current there is, more electricity flowing
• Current carries energy AND does work

8. Current
• Measured in amps (A)
• Circuit breakers in house regulate the amount
of current flowing through the wires
– Using too many appliances on a single circuit can
cause an excessive amount of current to flow
– If too much current is flowing through the
wires, they can get very hot and possibly start a
fire
– The circuit breaker is designed to trip before that
happens
• A fuse does the same thing, however circuit

10. Types of Current
1. Alternating current (AC)
– current that goes back and forth along the circuit
– Ex) electricity in house or school
– In the U.S., each wall socket has three wires that carry
120 volts
– When you plug something in, the current flows into
and out of the hot wire, through your appliance and
out through the neutral wire
– A third, ground wire is for safety. In case of a short
circuit the current flows through this wire and not you
• Used around water sources

11. 2. Direct Current (DC)
– This current only goes one direction
– Ex) Batteries

12. Resistance
• refers to how easily charges flow through an
object
– measured in ohms (Ω)
– The higher the resistance, the more difficult it is
for current to flow

13. Electrical Conductivity
• property of a material to allow charges to flow
– Things with high conductivity are generally
conductors
– Conductivity changes from material to material

15. Conductors
• Most wires are made of copper since allows
charges to flow through very easily
• Most metals are good conductors

16. Semiconductors
• Some materials with properties of both
– The invention of semiconductors allowed for the
technology that we all can’t live without today
(like computers)
– EX) Silicon

17. Insulators
• There are other materials block charges and
block current
– EX) Styrofoam, glass and plastic

18. Works Cited
• Hsu Ph.D., Tom. Foundations of Physical
Science. 1st ed. Peabody: Cambridge Physics
Outlet, 2002. 113-125. Print.
• Murray, Stephen. "Worksheets." Mr. Murray’s
Science Website: IPC Worksheets. N.p., 2009.
Web. 18 May 2012.
http://www.cstephenmurray.com/Acrobatfiles
/IPC/ch6to9/chap6no2.pdf