Gravitational Forces
Magnetic Forces
Electric Forces
Circuits
Electromagnetism
100
True or False: Gravity is ALWAYS a push, NEVER a pull
False
100
True or False: Magnetic force is ALWAYS a pull, never a push
False
100
True or False: The direction of the arrows in an electric field force diagram show how an electron would move in that field.
False
They show the direction a positive charge would move
100
What type of circuits are used in homes (series or parallel) and why?
Parallel
So equal power is supplied to all objects in the circuit and so that removing an object from the circuit won't break the circuit.
100
This scientist made the first electric motor
Michael Faraday
200
If you go to the moon, your _______ would change, but your _______ would stay the same.
If you go to the moon, your weight would change, but your mass would stay the same.
200
Why are only some materials magnetic? (Describe what's happening at the atomic level)
Give an example of a magnetic material
1) The spin on the atom's electrons don't all cancel each other out
2) Iron, Nickel, Cobalt, Neodymium
200
What 2 factors affect the strength of an electric force?
1) The charge of an object
2) The distance between objects
200
Why do metals make good conductors? (Discuss what is happening on the atomic level)
Electrons in metals form a shared "sea" of electrons that can move freely.
200
List three ways to increase the strength of an electromagnet.
1: More coils
2: More current
3: Place a magnetic material in the coils
300
Newton's Universal law of Universal Gravitation
The force of gravity between two objects is directly proportional to their masses and inversely proportional to the distance between them.
300
Where is the magnetic force the strongest on a magnet?
The poles
300
Which electric charges attract each other? Which charges repel each other?
Positive and Negative attract each other.
Positive repels Positive and Negative repels Negative.
300
Draw a circuit diagram for a parallel circuit with two bulbs, a battery and one switch that is open.
How would the brightness of the bulbs compare if they were in a series circuit?
The bulbs would be less bright in a series circuit because the voltage would be shared between the bulbs, in parallel each bulb gets the full voltage from the battery.
300
What is electromagnetism?
Phenomena where a moving electric field creates a magnetic field and a moving magnetic field creates an electric field.
400
What has more gravity, the Earth or the Sun? Why?
Why are we pulled toward the Earth and not the Sun?
The Sun has more gravity because it has more mass.
We fall toward the Earth because we are much closer to the Earth than the Sun, so the Sun's gravity does not affect us as strongly.
400
Why do compasses point North? Describe the forces involved
Earth has a magnetic field and the needle of the compass has a magnetic field. The south pole of the compass needle (which is colored to indicate N) will be attracted to the north pole of the Earth and will point in that direction.
400
What causes an object to have a positive charge? What causes an object to have a negative charge?
An object will be positive if it has more protons than electrons.
An object will be negative if it has more electrons than protons.
400
Describe each term and write the correct units:
Voltage:
Current:
Resistance:
Voltage is the measure of the electric force (Volts, V)
Current is the flow of electrons in a circuit (Amperes, A)
Resistance is the opposition to the flow of electrons in a circuit (Ohms)
400
Describe the forces that allowed this simple electric motor to move the wire coil.
When the circuit is completed an electric current moves through the coil which creates a magnetic field.
The magnetic field of the coil interacts with the magnetic field of the magnet sitting on the battery - when the poles are the same this pushes the coil away from the magnet causing it to move up.
When the circuit breaks the magnetic field in the coil goes away and the coil that is in motion will continue on its path and keep rotating.
500
A person has a mass of 60 kilograms. What is the person's weight in newtons on Earth?
Weight = (mass) (g)
W = (60 kg)(9.8 m/s2)
W=588 N
500
Draw a picture of 2 bar magnets that have their North and South poles facing each other. Include the magnetic field lines of each magnet and how they are interacting.
Are they pulling together or pushing apart? How can you tell?
Pulling together, the field lines connect the magnets.
500
What charge does object q have? How do you know?
It has a positive charge. You can tell because the electric field lines are radiating away from the object and electric field lines show the direction that a positive charge would move. Since like charges repel, this object must have a positive charge.
500
This circuit has a current of 1.5 amps and each bulb has a resistance of 2 ohms. Will a 6 volt battery be able to light the bulbs? Prove your answer mathematically.
No
V=IR
V= (1.5)(2+2+2) = 9 volts
500
Describe what you would observe on the meter when the magnet is moved in and out of the coils.
Is this AC or DC and how can you tell?
An electric current would be produced.
It is an AC current, you can tell because the direction of current would change depending on which way the magnet was moving.