Download Electricity Unit Review KEY

Mr. Storie
10F Science
Electricity Unit Review KEY
10F Science Electricity Review
KEY
1. Explain the difference between an insulator and a conductor.
Insulator holds electric charge in place (localized)
Conductor allows electric charge to travel through it
a. Give an example of an insulator. plastic, rubber, paper, glass…
b. Give an example of a conductor. metal, salt water
2. When testing an unknown charge, the only certain way to identify the type of charge is to observe its
repulsion with a known charge. Explain why.
Neutral objects attract both (+) and (-) electrically charged objects. Only a charged object will
repel a like charged object.
3. Draw a diagram (or a series of diagrams) to explain conduction. Add descriptions in your own words to
make it clearer.
1.
2.
3.
4.
Show a (-) charged object inducing charge separation in a neutral object
Show attraction of neutral object to charged object
Show contact and transfer of electrons from (-) charged object onto neutral object
Show repulsion as both objects now have (-) charges
4. True and False
F Static electricity occurs because charges build-up in one place on a conductor. insulator
T A neutral object will always attract to a charged object.
T An ampere is a coulomb of electrons move past a point per second.
T An excess of electrons results in a negative charge
F A series circuit has more than one conducting pathway for the current. parallel
F In a battery of identical cells connected in parallel, the voltage of the battery is equal to the total voltage
of all of the cells added up. series
F In a series circuit of Christmas tree lights, if one lamp burns out, only that lamp goes out. parallel
F Electrons move from the positive electrode to the negative electrode. Neg to Pos
Mr. Storie
10F Science
Electricity Unit Review KEY
5. Match the term on the left with the best descriptor on the right. Each descriptor may be used only once.
Term
Descriptor
E junction
A. more than one path for current to travel
D series circuit
B. a unit of energy measurement
A parallel circuit
C. a unit of power measurement
B joule
D. one path for current to travel
C watt
E. location where a circuit splits or reconnects
I insulator
F. rate of flow of current
V induction
G. can open or close a circuit
J conductor
H. the unit of resistance
H ohm
I. plastic wrapping on the outside of a power cord is an example
S current
J. metal is an example of this
T ammeter
K. charge that remains in one location
Q ampere
L. amount of electrical potential energy in a circuit
R series
M. a measure of energy use over time
G switch
N. relationship of voltage, current, and resistance
U electroscope
O. unit of charge (group of electrons)
O coulomb
P. slows down current and removes energy from a circuit
N Ohm’s law
Q. the unit of current
M power
R. a circuit where each thing is one after another
P resistance
S. the flow of electrons through a conductor
K static charge
T. a meter used to measure current
L voltage
U. device used to detect static electricity
V. charging an object using grounding
6. Draw the schematic symbol in the right hand
a. bulb
b. open switch
c. cell
●
●
- +
d. battery (3 cells)
e. ammeter
f. resistor
A
Mr. Storie
10F Science
Electricity Unit Review KEY
7. Draw a circuit diagram for the following representation:
8. Draw a circuit diagram of a parallel circuit consisting of a 9.0 V electrical source, an open switch
controlling the electron flow in the entire circuit, and three 5.0  resistors. Show the direction of
electrons.
e-
9. Draw a schematic diagram for a circuit made up of 2 cells in series, 3 lamps in parallel, a switch and an
ammeter.
10. Circle the best term in the brackets to correctly complete each statement.
a) A parallel circuit has (only one, more than one) path for current to travel.
b) Two different resistors are connected in parallel. The current through one of the resistors will be
(equal to, different from) the current through the other resistor. Electrons take the easiest path
c) If two different resistors are connected in parallel, the voltage across one resistor will be (equal to,
different from) the voltage across the second resistor.
Current is different (b/c resistance is too) but voltage is not
d) By adding a resistor in parallel with an original resistor, the total resistance of the circuit (increases,
decreases). More pathways for electrons makes for lower resistance
e) The total current entering the junction of a parallel circuit must be (equal to, different from) the sum
of the currents through each branch of the parallel circuit. Electrons in = electrons out
Mr. Storie
10F Science
Electricity Unit Review KEY
11. The switch on this circuit is closed. Which bulbs will be lit for each case?
(a) bulb 1 is removed all out
(b) bulb 2 is removed all out
(c) bulb 3 is removed 1,2,4,6,7
(d) bulb 4 is removed 1,2,3,5,6,7
(e) bulb 5 is removed 1,2,4,6,7
(f) bulb 6 is removed 1,2,3,4,5,7
(g) bulb 7 is removed all out
12. Calculate the missing potential difference in the following circuit diagram. The voltage at the source is
represented by VS.
VS = 110 V
all potential energy
(voltage) is lost over
the circuit – add it up
13. Calculate the current in the following circuit diagram. The current at the source is represented by IS.
I2 = 6 A
Total current splits at
the junction – 9+? = 15
14. A student measures the voltage of identical cells to be 6.0 V each. Indicate the voltage if
a. Two of these cells (at 6.0 V each) were connected in parallel 6 V
b. Four of these cells were connected in series
24 V
Mr. Storie
10F Science
Electricity Unit Review KEY
15. Find the unknown voltage at V, and current at A, in each of the following circuits.
a. Voltage = 10 V (adds up to 25 V)
Current = 3.0 A (same in any point in series circuit)
16. Consider the circuit diagram below.
voltage is the same in parallel resistors (current is different)
(a) Are the resistors in the above circuit connected in series or parallel? parallel
(b) Determine the voltage V, and the current A. 6.0 V 2.0 A (current splits, total must be 3.0A)
17. Three resistors, with a total resistance of 20 ohms, are attached in parallel. There is a cell and an
ammeter.
(a) Draw the circuit.
(b) If the cell offers 6 V of potential difference what is the current on the ammeter?
V = IR
I = V/R = 6 V/20 Ω = 0.3 A
18. If there is a current of 15 amperes in a circuit and 3 - (1.5V) cells connected in series. What will the
resistance be in this circuit?
R = V/I = (3 x 1.5 V)/15 = (4.5)/15 = 0.3 Ω
Mr. Storie
10F Science
Electricity Unit Review KEY
19. A portable CD player needs only 0.25 A of current. If the CD player is powered by a 9 V battery what is
the resistance in the current?
V = IR
R = V/I = 9/0.25 = 36 Ω
20. A clothes dryer in your home is attached to a 220 V source. The heating elements have a 12 Ω. What is
the current in the heating coils of the dryer?
V = IR
I = V/R = 220/12 = 18.3 A
21. A 25 mA current flows through a 300  lamp. What is the voltage across the lamp?
25mA x 1A/1000mA = 0.025A
V = IR = (0.025)(300) = 7.5 V
22. A portable CD player, operating with four 1.5 V batteries connected in series, provides a resistance of 15
k. What amount of current is flowing through the CD player?
15 k x 1000  / 1 k = 15000 
V = IR
I = V/R = (4x1.5)/15000 = 6/15000 = 0.0004 A
23. Two identical resistors are connected in series to a battery. How does the current through the second
resistor compare to the current through the first resistor?
A. half the current
B. no current
C. the same current
D. twice the current
24. Two identical resistors are connected in parallel to a battery. How does the voltage across the second
resistor compare to the voltage across the first resistor?
A. half the voltage
B. half the voltage of the battery
C. the same voltage
D. twice the voltage
25. Which correctly describes a load in an electric circuit?
A. It can turn the circuit on or off by closing or opening the circuit.
B. It is the source of electric energy.
C. It is the wire through which electric current flows.
D. It transforms electrical energy into other forms of energy.
26. Which is the correct calculation for electrical resistance?
A. the current across a load divided by the potential difference flowing through it
B. the current flowing through a load divided by the potential difference across it
C. the potential difference across a load divided by the current flowing through it
D. the potential difference across a load multiplied by the current flowing through it