# Science Electricity And Magnetism Test

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Describe one way that the force of gravity and magnetic force are similar. Describe one way they are different.
A similarity is they both exert force in their similar form. A difference is gravity always attracts, magnets attract and repel.
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Explain how there can be electrical charge inside matter even if it shows no electrical forces.
Atoms are made with equal amounts of positive and negative electricity charges so the attraction holds all the atoms in the mass together to hide the electric charge inside a state of mass.
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List one way electric current is similar to water current and one way that it is different.
They can both carry energy within themselves and do work. A difference is if a water pipe is open, water will leak out, if you cut open a current, it can't leak out.
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Explain the difference between an object that has "static electricity" and one that does not.
On a dry day if you touch an object that contains static electricity, you can get shocked, but with a different object you cannot be shocked.
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List the units for measuring current, voltage, and resistance
Voltage- volts Current- Amperes (amps) Resistance- Ohms
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Describe the difference between current and voltage. Can there be voltage without current? Can there be current without voltage?
Current flows while voltage provides the energy for the current flow. There can be voltage without current but you can't have a current without voltage.
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Electrical current flows:
From positive to negative
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An electrical circuit is:
A path for electric current to flow
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What is the difference between water in pipes and current in wires?
Water leaks out of open pipes but current does not leak out of open wires.
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How much electrical power is carried by 2 amps of current from a 1.5-volt battery?
3 watts
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How much current must flow to carry 240 watts at 120 volts?
2 amps
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Which carries more power: 100 amps at 12 volts or 10 amps at 120 volts? (Hint: Is one more, or are they equal?)
They are equal
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What happens to the current if a circuit's resistance increases?
It will decrease
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What happens to the current if a circuit's resistance decreases?
It will increase
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List the units used to measure resistance , voltage, and current. Give the abbreviation for each unit.
Resistance - R (Ohms) Voltage - V (Volts) Current - I (Amps)
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Classify each of the following as a conductor, semiconductor, or insulator: air, gold, silicon, rubber, and aluminum. Air- Gold- Silicon- Rubber- Aluminum-
Air- insulator Gold- conductor Silicon- semiconductor Rubber- insulator Aluminum- conductor
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Which magnetic pole is attracted to a south magnetic pole?
North magnetic pole
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Why can the magnetic force be either attractive or repulsive when gravity can only be attractive?
Because 2 of the same poles repel each other and you can switch magnetic poles.
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Name two materials which are magnetic and two that are not magnetic.
Magnetic: Safety pins, paper clips Non-Magnetic: fabric, plastic
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A compass points north because
It is facing earth's south magnetic pole.
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Why does a compass change direction when it is near a current-carrying wire?
The compass is attracted to the wire because the wire is a conductor.
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What is the difference between a permanent magnet and an electromagnet?
An electromagnet is caused by electricity and can be switched on and off, and a permanent magnet is magnetic without any energy.
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Iron attracts
both north and south poles of a magnet
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An electric generator uses changing magnetism to
induce current to flow in a coil
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2 kinds of electric charge
positive and negative
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2 magnetic poles
North and South
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The flow of tiny particles that carry electrical energy is called
an electric current
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The unit of measure for electric current is
amp
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A complete path through which electric current is
an electric circuit
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A(n) _________ has a high electrical resistance
insulator
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The physical law relating electrical resistance is called a(n) ___________
Ohm's Law
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A material, such as copper, with low electrical resistance is called a(n) ____________
conductor
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A magnet made using wires and electric current is an ____________
electromagnet
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Materials similar to iron that have strong magnetic properties are called ____________
ferromagnetic
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The influence created by a magnet that exerts forces on other material objects is known as a(n) _____________________
Magnetic Field
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A scientist says, "Magnetic poles of magnets and electric charges on bodies apply forces in similar ways." Explain what is meant by this statement.
They have similar effects on the object
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Why is it more difficult to determine the electric charge on an object than the mass of an object?
Electric charge is well hidden inside atoms, unlike mass.
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Explain how a cat's fur may become statically charged.
Static electricity comes from dry air. When a cat rubs against blankets, couches, carpets, etc., static accumulates on their fur. This happens because the cat is picking up excess negative charge that moves to the fur, and makes it stand.
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How does static electricity differ from current electricity?
Static electricity is a tiny imbalance between positive and negative charge on an object, and current electricity is a flow of tiny particles that carries electrical energy in wires and machines.
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Why don't you usually notice electric forces between objects?
You cannot see electric forces
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How does voltage cause current to do work?
Voltage provides power/energy for current to move.
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What does a battery do in an electrical circuit?
A battery provides the voltage, which provides the power/energy to make the current flow.
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Explain the difference between an open circuit and a closed circuit?
An open circuit is a circuit with a break in it, causing the current to stop flowing. A closed circuit is a circuit that is complete without a broken path.
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Will a bulb light in an open circuit? Why or why not?
No, because the current will not flow to the bulb, so the bulb will have no power to light.
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Is flipping a switch the only way to create an open circuit?
No, any kind of break in the circuit can cause an open circuit.
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How are volts, amps, and watts related?
Volts are in the battery which provided power/energy, amps measure the current, and watts measure the power of the current.
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Explain how volts, amps, and ohms are related in a circuit.
Volts provide power for the amps and the amps bring the energy to a light bulb and the light is measured in ohms.
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Why is it more dangerous to touch a wire conducting electric current with wet hands than with dry hands?
Water is a conductor, so when touching an electric current with wet hands, it could electrocute you, dry hands have more resistance.
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How does the force between two magnets differ from the force between two masses?
Two magnets attract or repel each other, and two masses don't attract or repel each other.
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Large, electromagnetic cranes are used in junk yards for moving scrap metal from one location to another. Why would an electromagnet be more useful in this application than a permanent magnet?
Electromagnets are stronger than permanent magnets, and in a junk yard you are moving big items, so you want a more powerful magnet.
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Suppose you stick a magnet on the door of your refrigerator. Is the magnet a magnetic material or a permanent magnet? Is the refrigerator door a magnetic material or permanent magnet?
The refrigerator door is a magnetic material, and the magnet is a permanent magnet.
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Two magnetic north poles _______ each other. Two south poles ________ each other. A north pole and a south pole __________ each other.
repel; repel; attract
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Magnetic field lines outside a magnet point away from its _______ pole and toward its _______ pole.
North; South
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Explain how to make current flow in a wire coil using a magnet.
A battery provides energy for the current to flow, so you change to magnet to an electromagnet.
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Compare an electric motor to an electric generator.
Electric motors transform electric energy into mechanical energy and electric generators transform mechanical energy into electrical energy.
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What happens when two positively charged objects are placed near each other?
They will repel each other
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Four 1.5-V AA batteries are connected end-to-end. 1) What is the voltage difference across a single battery? 2)What is the voltage difference across two batteries? 3) What is the voltage difference across all four batteries?
1.5 volts; 3 volts; 6 volts
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Household circuits in the United States typically run on 120 volts of electricity. Circuit breakers are commonly used to break a circuit if the current is greater than 15 amperes. What is the minimum amount of resistance needed in a circuit to prevent the circuit breaker from activating?
8 ohms
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A hair dryer draws a current of 10 A when plugged into a 120-volt outlet. What is the resistance of the hair dryer?
12 ohms
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Calculate the current produced if a 12-volt battery supplies 6 watts of power
0.5 amps
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A television runs on 120 volts and has a resistance of 60 ohms. What current does it draw?
2 amps
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The current flowing through a 1,200-watt hair dryer is 10 amperes. Calculate the voltage that must be supplied to operate this hair dryer properly.