A student built a simple electromagnet with copper wire, an iron bolt, and a 1.5-volt battery. The electromagnet was able to lift a paper clip from 3 centimeters away.
What action will decrease the strength of the electromagnet?
a
He can reverse the orientation of the battery.
b
He can use a thicker piece of copper wire.
c
He can use a longer piece of wire that wraps more times around the bolt.
d
He can replace the 1.5-volt battery with a battery of higher voltage.
The correct answer is D - He can replace the 1.5-volt battery with a battery of higher voltage. Increasing the voltage of the battery will increase the strength of the magnetic field generated by the electromagnet. The other options will either have no effect or will actually increase the strength of the electromagnet.
An electric motor uses regular magnets and an electromagnet to create motion. The attracting and repelling forces create rotational motion along with the electric current from the electromagnet.
What can a car manufacturer do to make an electric motor stronger?
a
A car manufacturer can remove coils from the electromagnet and decrease the size of the magnets causing the rotational motion.
b
A car manufacturer can remove coils from the electromagnet and increase the size of the magnets causing the rotational motion.
c
A car manufacturer can add coils to the electromagnet and increase the size of the magnets causing the rotational motion.
d
A car manufacturer can add coils to the electromagnet and decrease the size of the magnets causing the rotational motion.
The correct answer is C - A car manufacturer can add coils to the electromagnet and increase the size of the magnets causing the rotational motion. Adding more coils to the electromagnet will increase the strength of the magnetic field, and using larger magnets will also increase the strength of the motor. The other options involve decreasing either the size or number of coils/magnets, which would result in a weaker motor.
A mechanic dropped a bolt he needed to repair a car motor. He decided to make a simple electromagnet to try to attract the metal bolt. Which list of material would make the best electromagnet?
a
plastic rod for a core, copper wire, 9-volt battery
b
wooden rod for a core, copper wire, 9-volt battery
c
metal rod for a core, copper wire, 9-volt battery
d
glass rod for a core, copper wire, 9-volt battery
The correct answer is C - metal rod for a core, copper wire, 9-volt battery. The core of an electromagnet should be made from a ferromagnetic material, such as iron, nickel, or cobalt. A metal rod would be an appropriate material for the core. Copper wire would also be a good choice for the wire material, as it is a good conductor of electricity. The 9-volt battery would provide enough energy to create a magnetic field strong enough to attract the metal bolt. Plastic, wood, and glass are all non-magnetic materials and would not be effective as the core of an electromagnet.
Which of the following events is caused by magnetic force?
a
A person gets a shock from a doorknob after walking across carpet.
b
Pieces of clothing stick together after being in a clothes dryer.
c
The needle of a compass points toward Earth's North Pole.
d
Objects are constantly pulled toward the center of Earth.
The correct answer is C - The needle of a compass points toward Earth's North Pole. Magnetic force is responsible for the alignment of the needle with the Earth's magnetic field, causing it to point North. The other options describe electrostatic forces (causing a shock), static cling (caused by charges on clothing), and gravity (causing objects to be attracted towards the center of the Earth).
Which of the following is the process of charging a conductor by bringing it near another charged object and then grounding the conductor?
a
induction
b
neutralization
c
conduction
d
polarization
The correct answer is A - induction. Induction is the process of charging a conductor by bringing it near another charged object, without direct contact, and then grounding the conductor to transfer the charge. This causes the charges to redistribute within the conductor and results in a buildup of charge on one end of the conductor. Neutralization is the process of combining positive and negative charges to cancel each other out. Conduction refers to the transfer of charge through direct contact between objects, while polarization is the alignment of charges within an insulator due to an external electric field.
What is responsible for the distribution of charge in conductors and insulators?
a
number of protons
b
electron movement
c
number of electrons
d
proton movement
The correct answer is B - electron movement. Electrons are negatively charged particles that can move within a material. In conductors, the outermost electrons are free to move throughout the material, allowing for even distribution of charge. In insulators, the electrons are tightly bound to the atoms and are not free to move, which makes it difficult for charge to distribute throughout the material. Protons have a positive charge and are typically bound within the nucleus of an atom, so their movement is not responsible for charge distribution. While the number of electrons and protons in a material can affect the overall charge of the material, it is the movement of electrons that is responsible for the distribution of charge within the material.
Which occurs when neutral object A is charged by induction by charged object B?
a
Charges on object B are rearranged.
b
Charge transfers from object B to object A.
c
Charges on object A are rearranged.
d
Charge transfers from object A to object B.
The correct answer is C - Charges on object A are rearranged. When a neutral object (object A) is charged by induction by a charged object (object B), the charges in the neutral object are rearranged. This happens due to an electrostatic interaction between the charged object and the charges in the neutral object. The electrons in the neutral object will move in response to the presence of the charged object, causing a buildup of charge in one part of the object and a deficit of charge in another part. However, no actual charge transfer occurs between the two objects, so option B and D are incorrect. Option A is incorrect because the charges on object B do not rearrange in this process.
A student claims that the gravitational force between two objects depends upon the mass of the objects and the distance between them. Which argument best supports the student's claim?
If the distance between two objects increases, the gravitational force between the objects will decrease.
If the distance between two objects increases, the gravitational force between the objects will decrease.
If the distance between two objects increases, the gravitational force between the objects will increase.
If the distance between two objects increases, the gravitational force between the objects will increase.
If the distance between two objects decreases, the gravitational force between the objects will disappear.
If the distance between two objects decreases, the gravitational force between the objects will disappear.
If the distance between two objects decreases, the gravitational force between the objects will not change