Name______
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Electric Current Study Guide
(Multiple Choice Portion)
Physics
Electricity Test
Tuesday, May 7th
Format
Multiple Choice
Short Answer/Problem Solving
Multiple Choice Questions
1) Describe the components of an atom and the charge of each.
2) What is the difference between an insulator and a conductor? What causes this difference?
3) Describe voltage, resistance, and current. Give the units to measure each.
4) Write the formula for Ohm’s Law.
5) Name at least two components that are necessary to create a working electric circuit.
6) How are AC and DC different? What generates each type of electricity?
7) How is it possible for a squirrel to walk down a power line?
8) Give the units and formula for electrical power.
9) How does a series circuit impact voltages, resistances, and currents throughout the circuit?
10) How does a parallel circuit impact voltages, resistances, and currents throughout the circuit?
11) How does a series circuit behave if a light bulb burns out? Explain why!
12) How does a parallel circuit behave if a light bulb burns out? Explain why!
13) What is a short circuit?
14) What is the function of a circuit breaker?
15) What is the function of a GFI receptacle?
16) What are the major steps that a fossil fuel power plant goes through to generate electricity?
17) Describe the voltage that comes out of a power plant? Describe the voltage going into your house?
18) Complete the following table. (this is not a circuit – just math practice)
Voltage / Current / Resistance / Power12 V / 200 ohms
10 amps / 12 ohms
110 V / .2 amps
120 V / 660 W
3 amps / 48 W
19) Complete the following table for a series circuit.
Resistor size (R) in Ohms / Voltage (V) / Amperage (I)In amps
Resistor 1
/ 15 ohms / .02 ampsResistor 2
Resistor 3 / .7 volts
Resistor 4 / 10 ohms
RT / VT = 1.7 volts / IT
20) Draw the circuit from the table above
21) Complete the following table for a parallel circuit.
Resistance / Amperage / VoltageResistor 1
/ 10 ohmsResistor 2 / .3 amps / 6 volts
Resistor 3 / 20 ohms
Source / RT / IT / VT
22) Draw the circuit from the table above
Electric Current Study Guide KEY
(Multiple Choice Portion)
What is the difference between an insulator and a conductor? What causes it?
An insulator does not allow electricity to pass through, a conductor does allow electricity to pass through. An insulator holds on to its electrons tightly, so they can not move from one atom to the next, while conductors hold electrons loosely, so they can be passed from one atom to the next.
Describe voltage, resistance, and current. Give the units to measure each.
Voltage is the push of electrons, it is measured in volts (V)
Resistance is the push against the flow of electrons, it is measured in ohms (Ώ)
Current is the actual flow or movement of electrons, it is measured in amps
Write the formula for Ohm’s Law.
V=IR
Name at least two things that are necessary to create a working electric circuit.
A path for electrons to travel, made of some form of conductor.
A voltage source to push the electrons through the circuit.
Typically some load or device in the circuit to use the electricity.
How are AC and DC different? What generates each type of electricity?
DC, or direct current, has electrons only move in one direction (from the negative side to the positive side). It is created by batteries.
AC, or alternating current, has electrons moving back and forth in the circuit. It is created by a generator.
How is it possible for a squirrel to walk down a power line?
The squirrel is only touching one wire at a time, and not touching anything else, so there is not a circuit through him for the electricity to follow. If the squirrel were to step onto a tree branch while his back feet were still on the wire, he would be KFS (Kentucky Fried Squirrel).
Give the units and formula for electrical power.
Electrical power is measured in watts (W). P=VI
How does a series circuit impact voltages, resistances, and currents throughout the circuit?
In a series circuit, current is the same everywhere, voltage is split among all the resistors, and resistance adds up to make total resistance. The individual voltages also add up to the total voltage. Adding more resistance in the circuit decreases the current through the circuit.
Ohm’s Law can be used to find any individual voltage, current, or resistance; it can also be used to find total voltage, current, or resistance.
How does a parallel circuit impact voltages, resistances, and currents throughout the circuit?
In a parallel circuit, voltage is the same everywhere, current is split among the different paths, and resistance decreases more as more paths are added. The individual currents add up to the total current.
How does a series circuit behave if a light bulb burns out?
If a light burns out is a series circuit, the complete circuit goes out
How does a parallel circuit behave if a light bulb burns out?
If a light burns out in a parallel circuit, all of the other bulbs not in series with it will remain on.
What is a short circuit?
A short circuit is when electricity takes a “shorter” path, not through the intended circuit.
What is the function of a circuit breaker?
A circuit breaker helps protect people and stop overheating of wires by preventing an overload. Wires and machines are designed for a certain amount of current, too much is bad!! A 15 amp circuit breaker will shut off if more than 15 amps of current flow through it, stopping an overload of the circuit and overheating of wires.
What is the function of a GFI receptacle?
GFI, or Ground Fault Interrupt, is designed to shut itself off if electricity does not return to the outlet. This means that you can drop a toaster curling iron into a bathtub full of water, and no one gets electrocuted. (DON’T TRY THIS AT HOME!!)
What are the four steps that a fossil fuel power plant goes through to generate electricity?
1) Heat is generated by burning fuel
2) Steam is generated by the heat
3) The steam, under pressure, causes a turbine to spin
4) The spinning turbine causes the generator to spin
What are the voltages coming out of a power plant? going into your house?
A power plant puts out HUGE voltages (in the thousands) and these run down high voltage power lines.
Voltage is reduced to about 120 volts to go into your home.
Complete the following table.
Voltage / Current / Resistance / Power12 V / 12/200
.06 amps / 200 ohms / 12*.06
.72 W
12*10
120 V / 10 amps / 12 ohms / 120*10
1200 W
110 V / .2 amps / 110/.2
550 Ώ / 110*.2
22 w
120 V / 660/120
5.5 amps / 120/5.5
21.8 Ώ / 660 W
48/3
16 V / 3 amps / 16/3
5.33 Ώ / 48 W
1) Complete the following table for a series circuit.
Resistor size (R) in Ohms / Voltage (V) / Amperage (I)In amps
Resistor 1
/ 15 ohms / .3 volts / .02 ampsResistor 2 / 25 OHMS / .5 volts / .02 amps
Resistor 3 / 35 OHMS / .7 volts / .02 amps
Resistor 4 / 10 ohms / .2 volts / .02 amps
RT = 85 OHMS / VT = 1.7 volts / IT = .02 amps
2) Draw the circuit from the table above
3) Complete the following table for a parallel circuit.
Resistance / Amperage / VoltageResistor 1
/ 10 ohms / .6 amps / 6 voltsResistor 2 / 20 ohms / .3 amps / 6 volts
Resistor 3 / 20 ohms / .3 amps / 6 volts
Source / RT = 5 ohms / IT= 1.2 amps / VT = 6 volts
4) Draw the circuit from the table above