Download This quiz will cover ONLY Section 2

This quiz will cover ONLY Section 2-1. You will be asked to complete word problems, like the examples below. The
guide seems lengthy, but I wanted you to see exactly what we want to see on the quiz. Additionally, there will be a
matching section on vocabulary and a small section of fill in the blank on concepts to know.
V
I
R
Formulas:
V= voltage (volts)
I= current (amperes)
R= resistance (ohms)
To find current (I) use:
I= V
R
To find voltage (V) use:
V= I x R
To find ohms ( R ) use:
R= V
I
Sample Problems:
1. What is the current produced by a potential difference of 240 volts through a resistance of 0.2 ohms?
I=?
R= 0.2 ohms
V= 240 v
I=
0.2 ohms
240 v
I = 1,200 amps
2. What resistance would produce a current of 120 amps from a 6-volt battery?
R=?
I= 120 amps
V= 6 v
R= V
I
R=
6v
120 amps
R = 0.05 ohms
3. What voltage is necessary to produce a current of 200 ampeters through a resistance of 1 x 10 -3 ohms?
V=?
I= 200 amps
R = 1 x 10-3 ohms
V= I x R
**To solve this problem, it is best to convert 'R' to standard notation. Therefore, R would equal:
0.001 because when a number is changing from negatively the decimal point will move to the left the
amount of spaces as indicated. In this case, the original decimal point is after the number 1.
V= 200 amps x .001 ohms
V= 0.2 volts
**you should know how to convert from scientific notation to standard notation (moving the decimal left (negative
exponent) or right (positive exponent). The quiz will ONLY cover negative exponents.
Vocabulary:
Electrical potential: potential energy per unit of electric charge.
Potential difference: difference in electrical potential between two places. Provides the force that pushes charge through
a circuit. SAME as voltage
Electric Current: flow of electrons through a material
Voltage: causes current to flow through an electric circuit
Voltage source: creates a potential difference in electric circuit
Ohm: units of resistance
Voltmeter: measures voltage
Ammeter: measures amps (or current)
Concepts to know:

The greater the resistance, the less current there is for a given voltage

Resistance of a wire depends on the thickness and length of the wire

Electrons flow freely through conductors, but not insulators

Temperature affects electrical resistance

Currents will follow the path of least resistance when there are 2 paths

Ohm's Law: A conductor or any other device that has a constant resistance regardless of the voltage.
Resistance for most conductors doe not depend on the voltage across them.

Why does the light bulb not follow Ohm's law? Resistance increases when the bulb is turned on because the
filament has to heat up. Filament has lower resistance before heating, thus a cold filament conducts the most
current.