## Tuesday, 9 December 2014

### ELECTRICITY WORKSHEET

1. What voltage is required to make .250 A flow in a circuit with 8.00 ohms of resistance?
2. What current flows in a circuit with a potential difference of 12.0 V and a resistance of 25.0 ohms?
3. What is the resistance of a circuit with a voltage of 45.0 V and a current of 5.00 A?
4. A circuit has a total resistance of 80.0 ohms. What voltage will force 25.0 mA of current through it?
5. A 40.0 V circuit has a resistance of 80.0 ohms. What amount of current flows through it? How much power does the
circuit use?
Current______________________
Power________________________
6. 4.00 Amps flow through a circuit with resistance of 8.00 ohms. What is the potential difference of the circuit? How
much power is dissipated in the circuit?
Voltage______________________
Power________________________
7. How much current flows through the filament of a 75.0 W light bulb connected to a 120. V potential?
8. What is the resistance of an electric drill if its power rating is .500 hp if it is made to connect to 115 volts of potential?
(1 hp = 746 W)
9. A total resistance of 8.00 ohms is found in a loudspeaker. The current in its circuit is measured and found to be 1.40
A. What power is given off by the speaker? What potential difference will be used across the speaker terminals?
Power________________________
Voltage______________________

### ELECTRIC ENERGY , POWER, CURRENT PROBLEMS

Current Definition
1. 3.00 C of charge pass a point in a wire in 3.0 ms. How much current is this?
2. 3.00 X 1012 electrons pass a point in a wire in 0.0060 seconds. What is the current in the wire in
amps?
3. How many electrons pass a point in a conductor in 1 second if the wireʼs current is 0.05 amps?
Ohmʼs Law
4. The fuse for a car radio is a thin wire. The wire is made to burn apart is the current is too high?
What is the resistance of a fuse if it is to burn apart when 2.00 amps pass through it at 240 volts?
5. A light bulb is plugged into a wall outlet. It uses 0.68 A. What is the light bulbʼs resistance?
6. A flash light bulb is labeled to uses 1.77 A. Its resistance is 1.60 Ω. What voltage is the light bulb
rated for?
7 A flashlight light bulb is rated to take 2.83 Volts and use 0.300 amps. What is the resistance of
the filament?
8 Another flash light bulb is rated to use 0.300 A and has a resistance of 4.0 Ω. How much voltage
does this bulb use?
9 A stereo speaker has a resistance of 8.00 Ω. When it is operating at full power (exactly100 watts)
it uses 35 volts of electricity. What is the current drawn by the speaker?
10 A 100 watt light bulb draws 0.83333 amps from a wall outlet (120 volts). What is the resistance of
the light bulbʼs filament?
11 A toaster plugged into the wall, (120 volts), uses 14 amps of electricity. What is the resistance of
the the toaster?
12 The thermostat in a house turns o and off the air conditioner and furnace using 24 volts. What is
the current in the thermostat when it is turned on it if draws 0.100 amps?
13 A motor in a radio control car uses 7.2 volts and draws 14.4 amps of electricity. What is the
resistance of the motor?
14 The volume knob on a radio varies the resistance on a line that goes to the speakers. At a low
volume the resistance is 10,000 Ω. At a high volume the resistance is 10 Ω. If the stereo
maintains 35 volts into the speaker then, what are the two currents going into the speaker?
Current Electricity Basics Worksheet
15 When a battery “dies” the resistance inside the battery rises while the voltage it can produce
almost always remains the same. A new 1.5 volt alkaline battery has a resistance of 0.15 ohms.
an older battery may have a resistance of 15 Ω. how much current is drawn by a new and old
battery?
16 The resistance of dry human skin is about 500,000 Ω and wet, sweaty, human skin is about
1000 Ω. How much current passes across someoneʼs fingers if they touch the leads of a 9 volt
battery when their skin is wet or dry?
17 0.010 Amps causes involuntary muscle contractions. How much voltage is required to cause
involuntary muscle contractions on wet and dry skin?
Power
18 A watch battery is produces a voltage of 1.5 volts. How much power is used by the watch if it
draws 0.001 A?
19 A high tension power line carries 1,000,000 volts of electricity. If the line of to carry 200 Aʼs, then
how power does the power line carry? What is the resistance of the power line?
20 A battery is rated at 1.5 volts. This battery can produce a maximum of 15 W of power.
• How much current can this battery produce?
• What is the resistance of the wire attached to the battery ?
21 A stereo speaker is rated at 8 ohms and 40 watts. A fuse is going to be installed in the speaker.
The fuse can only handle a certain amount of current at 240 volts. How much current does the
fuse need to handle if it is to “blow” at 40 watts?
22 A radio control car uses 7.2 volts and 14 amps. How much power is used by the car?
23 What are the resistances of a 50, 100 and 150 watt light bulb that is plugged into a wall outlet ,
120 volts?
24 A shorted out 12 V car battery can generate 4800 amps! (Never do this. a shorted out battery will
explode.) What is the batteries resistance and how much power is generated by the battery
before it explodes?
25 A hair dyer says it generates 1400 watts. It is plugged into a wall outlet, 120 volts. What is the
current drawn by the hair dryer and what is its resistance?
26 On most home each circuit in a house can handle 15 amps at 120 volts. How much power is
this? Will a 1400 watt hair dryer and four 75 watt light bulbs blow this circuit?
27 The heating element on a stove is connected to a 240 V outlet. The element draws 20 amps
when it is turned on. What is the resistance and power of the element?
28 A motor on a band saw can generate 1/2 horsepower on high. If the motor is plugged into a wall
outlet, how much current will it require? (746 W = hp)
Current Electricity Basics Worksheet
29 The garbage disposal in a sink can generate 3/4 horsepower. If the disposal is plugged into a wall
outlet. How much current does it draw?
30 A small car can generate 95 hp. An equivalent electric vehicle is to be built such that it can
generate the same power as its gasoline counter part. If the electric vehicleʼs motor uses 12
volts, then what is the resistance of the motor? What is the current drawn by the motor? How
many charges are moved by the current if the car runs for 1 hour?
31 What is the current drawn by a household clock-radio using 12 watts?
32 A fan draws 0.184 amps while connected to a wall outlet. What is the power rating of this fan?
33 What is the current drawn by a hair dryer using 1500 watts?
34. What is the current drawn by car stereo that is connected to the car's 12.0 volt battery, if the car
stereo draws 40 watts?
35. What is the battery voltage of a portable radio that draws 0.500 amps and is rated at 1.5 watts?
36 You've just invented a "Do-Hickie" that uses 3.0 volts and draws 3.0 amps. What is the power
37 What is the power rating of a household light bulb that draws 0.60 amps?
38 For the same fuse in problem #4, how much current would it take to burn apart the wire inside
the fuse if it were connected to a 120 volt or a 12 volt source?
39 Stereo speaker is rated to take 100 watts. If the speakerʼs resistance is 8 Ω, How much voltage
is used by the speaker?
40 What is the power rating of a space heater that draws 9.6 amps while connected to a wall outlet?

### PHYSICS QUESTIONS ENERGY AND LIGHT

1. A swimmer climbs out of a swimming pool on a warm, dry day. Almost immediately he begins
to feel cold.
Why is this?
A The water allows a convection current to remove heat from his skin.
B The water takes latent heat from his body in order to evaporate.
C The water on his skin is a good conductor of heat.
D The water prevents infra-red radiation from reaching his body.
2. A substance consists of particles that are close together and moving past each other at
random. The average speed of the particles is gradually increasing.
What best describes the substance?
A a liquid being boiled to form a gas
B a liquid being heated
C a solid being heated

D a solid being melted to form a liquid
3. In a hydroelectric power station, water from a reservoir falls down a long pipe before entering
The turbines. The turbines then turn the generator.
What is the overall energy conversion?
A electrical energy into kinetic energy
B electrical energy into potential energy
C kinetic energy into chemical energy
D potential energy into electrical energy
4. Some of the more energetic molecules in a liquid leave the surface, leaving the rest of the
Liquid slightly cooler.
What is the name given to this process?
A boiling
B condensation
C evaporation
D freezing
5. When we talk about angles of incidence and reflection, we often talk about the normal. The normal to a surface is an imaginary line that is perpendicular to the surface. The normal line starts where the incident ray strikes the mirror. A normal line is drawn for you in the sample problem above.
a. Draw a diagram that shows a mirror with a normal line and a ray of light hitting the mirror at an angle of incidence of 60 degrees.
b. In the diagram above, label the angle of reflection. How many degrees is this angle of reflection?
6. Light strikes a mirror’s surface at 20 degrees to the normal. What will the angle of reflection be?
23.1
7. A ray of light strikes a mirror. The angle formed by the incident ray and the reflected ray measures 90 degrees. What are the measurements of the angle of incidence and the angle of reflection?

8. In a game of basketball, the ball is bounced (with no spin) toward a player at an angle of 40 degrees to the normal. What will the angle of reflection be? Draw a diagram that shows this play. Label the angles of incidence and reflection and the normal.
Use a protractor to figure out the angles of incidence and reflection for the following problems.

### ELECTRICITY AND ENERGY RESOURCE QUETIONS

1 a) What do you mean by Fossil fuels?

b)    How do you think that fossil fuel may affect the Environment?

2. What are the energies that are not depend on Solar energy?

3.a) What is the use of Resistor in the circuit?

b)Name any three electrical component that uses resisto

4.  What are three benefits or advantages of hydropower?

5.  Differentiate between Solar and Wind energy

6.Draw the diagram in the following situations

a)                  A circuit containing two bulbs and one cell in series.

b)   A circuit containing 4 bulbs, a switch, two cells in series and a voltmeter measuring the voltage across one of the bulbs.

7. Write down the three ways in which heat may he transferred from one place to another

8. Which of the following is the worst conductor of heat?
air copper vacuum glass rubber stee

9. How is heat transferred by conduction

10. Which is the better conductor, a solid rod of copper or a hollow rod of copper of the same length and diameter

11. Which of the following metals is the best conductor of heat?
silver   steel   aluminium   copper

12. Why do people wear layers of clothing in the winter and birds fluff up their feathers to keep themselves warm?

13. By what process is heat transferred down a metal rod?

10 Explain the following:
(a) saucepans for use on a hot plate are made with copper bottoms;
(b) these bottoms are made as flat as possible;
(c) the handle of the saucepans are made of wood or plastic