8.2.1-Magnetic Force

​8.2.1-Magnetic Force

By Jessica Freeman

Magnetic Force

Multiple Choice

Suki was investigating magnetism with two bar magnets. She finds that her magnets stick to some surfaces like the refrigerator door, the sink, and the window frame. The magnets did not stick to the window glass, the door, or the wall.

What types of material attract a magnet?

• materials containing any type of metal

• materials that are shiny

• materials that contain iron

• materials that contain another magnet

​Explanation

​The correct answer is “materials that contain iron.” While magnets are attracted to some types of metal (such as iron, nickel, and cobalt), not all metals are attractive to magnets (such as copper, zinc, and aluminum). An object’s shine is not related to whether it will attract a magnet. Materials that contain a magnet may either be attractive or repulsive, depending on which poles come in contact with each other.

Multiple Select

Suki was investigating magnetism with two bar magnets. She finds that her magnets stick to some surfaces like the refrigerator door, the sink, and the window frame. The magnets did not stick to the window glass, the door, or the wall.Next, she decides to investigate their magnetic force. What tests could she perform to determine which magnet has a stronger magnetic force? Choose the two that apply.

• Put both magnets on a refrigerator door, and test which requires more force to pull it off the door.

• Put them next to each other, and test how much force is required to separate the two magnets.

• Pour iron filings onto both magnets while they are close together and see which magnet collects the largest pile of filings.

• Pour iron filings onto both magnets while they are apart and see which filings arrange into lines that are closer together.

​Explanation

​The correct answers are “Put both magnets on a refrigerator door, and test which requires more force to pull off the door” and “Pour iron filings onto both magnets while apart and see which filings arrange into lines that are closer together.” Putting the magnets together and trying to pull them apart does not test the individual strength of each magnet, so it cannot be used as a test to determine which has a stronger magnetic force. Similarly, if the magnets are together, the iron filings will follow the magnetic lines of the combined magnetic force of both magnets instead of being attracted to each magnet individually.

Multiple Choice

Naji was using his computer to model the strength of the magnetic field around a bar magnet. He knows that certain parts of the magnetic field are stronger than others. Where are the strongest and weakest parts of the magnetic field shown in the diagram?

• strongest: A, weakest: B

• strongest: A, weakest: D

• strongest: C, weakest: A

• strongest: C, weakest: B

​Explanation

​The correct answer is “strongest: C, weakest: D.” Although A is centered on the pole, it is further away from the magnet than point C and is therefore weaker. Point B and D are both weaker than either point A or C. Point B is further away from the magnet than D and therefore is weaker.

Multiple Choice

Justin was creating a chart comparing the potential energy between charged particles and the potential energy of magnets. Which of the following is true?

• The potential energy between both like charges and like poles increases as they move closer together.

• The potential energy increases between like charges and decreases between like poles as they move closer together.

• The potential energy between both like charges and like poles decreases as they move closer together.

• The potential energy decreases between like charges and increases between like poles as they move closer together.

​Explanation

​The correct answer is “The potential energy between both like charges and like poles increases as they move closer together.” For both electric and magnetic potential energy, like charges or poles moving closer results in increased potential energy. Moving like charges and poles farther apart results in decreased potential energy, based on their naturally repelling properties. For both electric and magnetic potential energy, opposite charges or poles moving closer results in decreased potential energy. Moving opposite charges farther apart results in increased potential energy, based on their naturally attractive properties.

Examples of

Multiple Choice

Why are some forces considered to be noncontact forces?

• Objects must be far apart in order to exert a force.

• Objects push each other apart to increase the distance between them.

• Objects do not have to touch each other to experience a force.

• Objects must be large in size in order to exert a force that is strong enough to notice.

• Magnets have two poles, north and south, where the forces are the strongest.

• Opposite poles attract, or pull, on each other.

• Like poles repel, or push away from, each other.

• All magnets have an invisible magnetic field.

• The strength of magnetic forces depend on distance and materials.

​

Magnetic Forces

Multiple Choice

What are two factors that affect the strength of magnetic forces?

• poles and gravity

• distance and material

• distance and direction

• electricity and gravity

Multiple Choice

A magnetic field of a magnet gets _____________ the further magnetic object moves away from the magnet.

• positive

• weaker

• negative

• stronger

• Is a push or pull between charged objects.

• Static electricity is a buildup of electrical charge on an object.

• Objects can have a positive or negative charge depending on their number of electrons (-).

• Like magnets, same or like charged objects repel, while opposite charged objects attract.

​

Electric Forces

Multiple Choice

Electrical charge built up on the surface of an object is called _________________.

• current electricity

• lightning

• electrons

• static electricity

Multiple Choice

Negative and positive charges repel.

• True

• False

Magnetism is a Force

Understanding the Push and Pull of Magnets

Electricity and Magnetism

Static Electricity

Building Electric Charges

Multiple Choice

________ ______ is a matter with a surplus or deficiency of electrons.

• Interacting Objects

• Charged Object

• Electromagnetic Force

• Magnetic Fields

Electric Charge and Static Electricity

Electric Forces

Science 7/8

Electric Fields

• An electric field is a region around a charged object where the object's electric force is exerted on other charged objects.

• Because positive charges are repelled by positive charges.. and attracted to negative charges..field lines point away from positive charges and towards negative charges

How Does Charge Build Up?

• Most atoms are uncharged, or neutral because the protons equal the electrons.

• Uncharged objects become charged by gaining or losing electrons

• Static electricity is the buildup of charges on an object

• In static electricity, charges build up on an object, but they do not flow in a current

Charging Objects

• Charges are neither created nor destroyed. This is known as the law of conservation of charge.

• If one object loses electrons, another object must pick them up

• There are four methods by which charges can redistribute themselves: Friction, conduction, induction, polarization

• 
  

Charging by Friction

• Charging by friction is the transfer of electrons from one uncharged object to another by rubbing objects together

• 
  

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Charging by Conduction

• When a charged object touches another object, electrons can be transferred

• This is the process of transferring electrons by direct contact

Charging by Induction and by Polarization

• Electrons can react to the electric field of a charged object without touching the object itself. This is induction

• Polarization occurs when electrons move only within their own atoms. In this case, the electrons create charged ends of the atoms

Multiple Choice

True or False:
In static electricity, charges build up on an object, but they do not flow continuously.

• True
• False
• 11
• Tuesday

Multiple Choice

Rubbing a balloon on hair is an example of static charge build up created by....

• conduction
• friction
• induction
• hairduction

Multiple Choice

The girl's hair and the comb are attracting  one another.  The hair and the comb have

• opposite charges
• like charges

Multiple Choice

If an object has the same number of positive and negative charges, its electrical charge is...

• positive
• negative
• neutral or no charge
• opposite

Multiple Choice

An object becomes postiively charged when which of the following occurs?

• loses electrons
• gains electrons
• loses protons
• gains neutrons

Multiple Choice

What is static electricity caused by?

• A balance of power

• A balance of positive and negative charges

• An imbalance of positive and negative charges

• An imbalance of protons and neutrons

Multiple Choice

Which of the following is caused by static electricity?

• a stove getting hot when it is turned on
• a magnet being attracted to a refrigerator
• a lightning strike during a storm
• a light bulb coming on when a switch is turned on

Multiple Choice

What happens when you touch a metal doorknob after rubbing your shoes on the carpet?

• The doorknob sends a burst of electric current into your body
• Millions of electrons go from your finger into the doorknob
• The doorknob sends millions of electrons into your finger
• our finger becomes negatively charged

Multiple Choice

If a substance has a higher number of electrons than protons on its surface, what type of charge does it have?

• A positive charge.
• A negative charge.
• A neutral charge
• No charge at all

Multiple Choice

Mrs. Davis rubbed two balloons with a piece of wool. What will happen when the balloons are brought near each other?

• The balloons will repel each other.

• The balloons will attract each other.

• The balloons will become positively (+) charged.

• The balloons will pop.

Multiple Choice

Having the tendency to pull other objects toward itself.

• Interacting

• Charged

• Attractive

• Magnetic

Multiple Choice

A particle with either positive or negative electrical charge.

• Neutral Particles

• Charged Particle

• Attractive Particles

• Magnetic Particles

Multiple Choice

A directional flow of electrical charge through an object or medium

• Current

• Magnitude

• Attractive

• Magnetic

Multiple Choice

Attractive or repulsive interaction between any two charged objects.

• Electric Force

• Potential Force

• Kinetic Force

• G-Force

Multiple Choice

A force consisting of both an electric component and a magnetic component, created by an electric current or moving electrical charge.

• Electric Force

• Electromagnetic Force

• Electrokinetic Force

• G-Force

Multiple Choice

Objects that affect one another

• Electric Force

• Electromagnetic Force

• Interacting Objects

• G-Force

Multiple Choice

The area around a magnet or moving electrical charge that can exert a magnetic force.

• Electric Force

• Electromagnetic Force

• Corn Field

• Magnetic Field

Multiple Choice

A force that attracts or repels objects toward or away from each other; caused by electrons in a substance

• Magnetism

• Parasitism

• Gravity

• Positivity

Multiple Choice

The size or quantify of something

• Depth

• Width

• Length

• Magnitude

Multiple Choice

Having the tendency to push other objects away from itself

• Repulsive

• Negate

• Evacuate

• None of the above

Multiple Choice

When two _____ charged metal objects are pushed closer together, their repulsive force _________,

• positively, increases

• alike, increases

• negatively, decreases

• alike, decreases

Multiple Choice

When magnetic poles that are _________ align, they will have an attractive force.

• opposites

• alike

• greater

• negative

Multiple Choice

When the currents of two electromagnets are increased, the size of the _____ is increased.

• magnet

• force

• charge

• opposite

Multiple Choice

Objects that are _______ exert forces on each other,

• magnetic

• forced

• charged

• opposite

How Does It Happen?

• Electric Charges Build Up (Friction causes electrons to build up on an object)

• Then JUMP (ZAP)!

• The JUMP is called Static Discharge

Multiple Choice

When friction between two objects causes electrons to build up on one object it is called

• electric charge

• electric force

• electric drive

• gravity

Multiple Choice

When electrons suddenly jump from the object they have built up on that is called static discharge.

• True

• False

Where Does It Happen?

• Anywhere electric charge build up.

• Natural electricity

Multiple Choice

Static electricity is the _______________ form of electricity.

• human-harnessed (man-made)

• natural

Multiple Choice

Where does static electricity happen?

• where there are electrical wires

• anywhere electric charges build up

• only in outer space

• underground

Example of Static Electricity

• Lightning

• Negative Particles in Clouds JUMP to Positive Areas - Opposites Attract

• Static Discharge

Multiple Choice

Lightning can only travel from the sky to the ground.

• True

• False

Multiple Choice

Lightning happens when there is

• static discharge

• static distancing

• electric fencing

• not enough electric charge

Example of Static Electricity

Shocks

Build Up of Electrons on You Suddenly JUMP to a Metal

Static Discharge

Multiple Choice

On dry, winter days, you feel a shock when

• extra neutrons jump off your body onto a metal object

• extra electrons jump off your body onto a metal object

• extra protons jump off your body onto a metal object

Multiple Select

Click all that are examples of getting an electric shock from static electricity.

• person shocking another person by touching them

• person getting shocked by touching metal frame as they are getting off a trampoline

• person getting shocked by grabbing an electric fence

• person getting shocked by holding a live electrical wire

Example of Static Electricity

Static Cling

One object has a negative electric charge (gained electrons), one object has a positive electric charge (lost electrons) - Opposites Attract

Multiple Choice

Electric force causes electrically charged objects with opposite charges to

• attract

• repel

Multiple Choice

All examples of static cling happen in a clothes dryer.

• True

• False

Example of Static Electricity

Hair Stands Up

All hairs have extra negative electrons and push apart from each other causing hair to stand (likes repel)

Multiple Choice

In order for static electricity to cause your hair to stand up, your hairs must all have the

• same charge

• different charges

• no charge at all

Multiple Select

Which of these activities could cause static electricity to make your hair stand up?

• jumping on trampoline

• sliding down a slide

• pulling a sweater over your head

• touching a Van de Graaff generator