Download Winter Final Review with answers

Winter Trimester Physics Final Review
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Does an object need to be grounded to charge it by induction? No
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A 10-ohm resistor has a 5-A current in it. What is the voltage across the resistor? 50 V
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A 60-watt light bulb is connected to a 120-V outlet. How much current exists in the light bulb? 0.5 A
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To be safe in the unlikely case of a lightning strike, it is best to be inside a building framed with
_metal_.
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What can be said about the voltage across a simple parallel circuit? The voltages are equal.
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When a 10-V battery is connected to a resistor, 2 A of current flows in the resistor. What is the
resistor's value? 5 ohms
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What is the resistance of a toaster that uses 2 A of current when connected to a 120-volt power source?
60 ohms
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What can be said about electrons in a good insulator? They are tightly bound to the atoms.
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Two like charges _repel_ when near each other.
10. What happens to all of the light bulbs in a series circuit when one light bulb burns out. They all go out.
11. An electroscope is charged positively, as shown by foil leaves that stand apart. As a negative charge is
brought close to the electroscope, the leaves _repel less_.
12. The primary reason a bird can perch harmlessly on bare high voltage wires is that _there is not
difference in potential energy_.
13. The SI unit of charge is the _Coulomb_.
14. What type of current, ac or dc, is produced by a battery? DC
15. The charge of an electron is - 1.6 x 10-19 C.
16. True or false: Lightning can occur between cloud to cloud and cloud to ground. True.
17. Power outlets in our homes typically have a potential difference (voltage) of __120 V_.
18. When connected to a 120-volt power supply, how much current exists in a light bulb that has a
resistance of 240 ohms? 0.5 A
19. When protons and electrons are near each other they will _Attract_.
20. What are the different methods with which objects can be charged? Friction, Conduction, Induction.
21. Coulomb's law says that the force between any two charges depends on what two factors? Distance
between charges and the amount of charge.
22. A 2-C charge and a 4-C charge attract each other with 10 N of force. How much will a 2-C charge and an
8-C charge attract each other when placed the same distance apart? 20 N
23. A negatively charged rod is brought near a metal can that rests on a wood table. You touch the opposite
side of the can momentarily with your finger. The can then has what charge? Positive
24. How much power is used by a 6.0-V flashlight battery that draws 0.5 A of current? 3 W
25. Where do the electrons come from that produce heat and light in a light bulb? From the bulb itself.
26. If you comb your hair and the comb becomes positively charged, your hair becomes _negatively_
charged.
27. In solid conductors, what flows when there is an electric current? Electrons
28. When plugged into a 120-V wall outlet, how much current is used by a toaster rated at 1200 W? 10 A
29. Electrical forces between charges are normally strongest when the charges are _Closest together__.
30. Why are metals such good conductors of electricity? They have free electrons.
31. Electrical resistance is measured in _Ohms__.
32. Two charges separated a distance of 1 meter exert a 1-N force on each other. If the charges are pulled to
a 2-m separation distance, the force on each charge will be _0.25 N_.
33. Compared to thin wires, electrical resistance in thick wires is _Less_.
34. Particle A has twice as much charge as particle B. Compared to the force on particle A, the force on
particle B is _The same_.
35. Bring a charged object near a conductor and then momentarily touch the conductor. This demonstrates
charging by what process? Conduction
36. For most conductors, as their temperature increases, their resistance _increases_.
37. When the distance between two charges is halved, the electrical force between the charges
_Quadruples_.
38. Two charges separated a distance of 1 meter exert a 1-N force on each other. If the magnitude of each
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charge is doubled, the force on each charge is _4x larger_.
What are fuses and circuit breakers used for in household circuits? To protect from fires due to the
overloading of current in a circuit.
The current through a 10-ohm resistor connected to a 120-V power supply is _12 A_.
When a charged cloud passes overhead, the ground below is charged by what process? Induction
A woman experiences an electric shock. The electrons making the shock come from where? The
woman.
Why will a charged balloon will stick to a wall?
What does the electrical resistance in a wire depend on? The thickness of the wire, the length of the
wire and the material from which the wire is made.
Two charged particles held close to each other are released. As they move, the force on each particle
increases. Therefore, the particles have what sign? Opposite
What particles are in the atomic nuclei of almost all atoms? Protons and neutrons
What is the definition of electric power? The rate at which energy is used.
What is an ampere? An ampere is the unit for electric current. It is the number of coulombs that
flow per second.
When resistors are put in parallel with each other, what happens to their overall resistance? It drops.
What is the symbol used to represent resistance in a schematic diagram? A zigzag line.
What is the source of all magnetism? The motion of charged particles.
If the north pole of one magnet is brought near the south pole of another magnet, the poles will do
what? They will attract.
What happens if you break a bar magnet in half? You will get two equal magnets with north and
south poles.
If you put a small compass in a magnetic field, the compass needle will do what? The compass needle
will align with the Earth’s magnetic field.
Where is a magnetic field strongest around a magnet? At the poles.
What produces magnetic fields? The motion of charged particles.
What are magnetic domains? Regions in a material where the spins of the electrons is aligned.
What is the earth's magnetic field is most likely due to? The motion of the charged particles in the
liquid outer core.
The earth's magnetic field reverses its polarity about once every _one million_ years.
Which geographic pole of the earth is nearest the magnetic north pole of the earth? South geographic
pole
Which pole of a compass needle points to a south pole of a magnet? North pole
Magnetic field lines surrounding a magnet are conventionally drawn from _North_ to _South__.
What is the definition of electromagnetic induction? A changing magnetic field induces a current in
a loop of wire.
A device consisting of a coil that is mechanically rotated in a stationary magnetic field is called a
_electric generator_.
What energy source is used to turn most commercial generators? Steam
What is the definition of speed? The rate of change of distance.
What are some possible units of speed? Km/hr, mi/hr, m/s
What does the speedometer of a moving car measure? Instantaneous speed.
What is the definition of acceleration? The rate of change of velocity
An object travels 8 meters in the first second of travel, 8 meters during the second second of travel, and
8 meters again during the third second. What is its acceleration? Zero.
Ten seconds after starting from rest, a car is moving at 40 m/s. What is the car's average acceleration?
4 m/s/s.
What happens to an object’s acceleration and velocity as it freely falls in a vacuum? The acceleration is
constant.
In the absence of air resistance, do objects fall at constant acceleration? Yes.
A ball is thrown upwards and caught when it comes back down. In the absence of air resistance, the
speed of the ball when caught would be greater than, less than or equal to the speed of the ball when
thrown. The same.
A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point.
During this time the acceleration of the ball is always what value? 10 m/s/s.
76. When a basketball player jumps to make a shot, once the feet are off the floor, the jumper's acceleration
is what value? 10 m/s/s.
77. Suppose you take a trip that covers 240 km and takes 4 hours to make. Your average speed is __60
km/hr_.
78. Suppose a car is moving in a straight line and steadily increases its speed. It moves from 35 km/h to 40
km/h the first second and from 40 km/h to 45 km/h next second. What is the car's acceleration? 5
km/h/s
79. A ball is thrown straight up. At the top of its path its instantaneous speed is _zero_.
80. A ball is thrown straight up. At the top of its path its acceleration is _10 m/s/s_.
81. A car accelerates at 2 m/s/s. Assuming the car starts from rest, how much time does it need to
accelerate to a speed of 30 m/s? 15 s.
82. If an object were equipped with a speedometer and allowed to fall freely on a planet where the
acceleration due to gravity is 20 m/s/s, the reading on the speedometer increases each second by
_20/m/s__.
83. Ten seconds after starting from rest, a freely falling object near the earth's surface will have a speed of
about _100 m/s__.
84. If you drop a feather and a coin at the same time in a vacuum tube, which will reach the bottom of the
tube first? They will reach at the same time.
85. If a projectile is fired straight up at a speed of 10 m/s, the total time to return to its starting point is
about _2 seconds_.
The next fifteen questions are true or false.
86. Magnetic poles are similar to electric charges in that they both can repel and attract one another. True
87. Just as it is easy to separate electric charges, it is relatively easy to isolate a magnetic monopole. False
88. A magnetic field is produced by the motion of charged particles. True
89. Spinning electrons themselves are small magnets. True
90. Magnetic domains are regions in a material where clusters of atoms are randomly magnetized. False
91. The magnetic pole in the Northern Hemisphere is located at the geographic North Pole. False
92. The rate at which distance is covered is called speed. True
93. Average speed is defined as the time it takes for a trip divided by the distance. True
94. Velocity is different from speed in that velocity is speed in a given direction. True
95. The SI unit of velocity is the meter. False
96. The rate at which velocity changes with time is called acceleration. True
97. The SI unit of acceleration is meters per second. False
98. When a car rounds a corner at a constant speed, its acceleration is zero. False
99. Even though a car is slowing down, it is still accelerating, in the most general definition of acceleration.
True
100. A ball is thrown into the air. At the highest point, the ball has zero velocity and zero acceleration. False
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