Electromagnetism Created by Craig Smiley (Harrison HS, West Lafayette, IN) Supported by grant PHY-0851826 from the National Science Foundation and by Purdue University

Magnetic Field Lab & Rubbing Nail Lab Lesson 1 - Magnets Magnetic Field Lab & Rubbing Nail Lab

Magnetic Field Lines Which is a correct diagram of the magnetic field lines in and around a bar magnet? A. B. C. D. N S N S N S N S

Permanent Magnets A magnet can attract what materials? Any materials that have an electric charge Any material that is a conductor Any metal Only materials that have ferromagnetic elements in it Only other magnets

Permanent Magnets A magnet can repel what materials? Any materials that have an electric charge Any material that is a conductors Any metal Only materials that have ferromagnetic elements in it Only other magnets

Lab Follow-up An un-magnetized nail is brought near a magnet as illustrated. What pole with the head become? North South Either Neither

Lab Follow-up What magnetic pole will the tip of the nail have after being rubbed with a magnet as illustrated? North South Can’t be determined

Lab Follow-up Which two ways will could you rub a nail with a magnet to make the pointed tip of the nail the North pole? A) 1 & 2 B) 1 & 3 C) 1 & 4 D) 2 & 3 E) 2 & 4

Permanent Magnet What would happen if you cut a bar magnet in half? A. B. C. D. The magnet would be broken making it two totally unmagnetized pieces of metal. E. None of these

Permanent Magnets What would a cause a magnet to be stronger than another magnet? It could be bigger, thus increasing the total number of domains It could have a higher percentage of domains pointing the same direction It could have more densely packed domains, thus increasing the number of domains Two of these All of these

Permanent Magnets What would cause a magnet to become demagnetized? Cut it in two Heat it Beat it against something Two of these (A, B, C) You can’t demagnetize a magnet

Geomagnetism If we had a magnet that was able to spin freely (as though floating in a tub of water), which geographic direction would the south pole of the magnet point? A) North B) South C) Can’t be determined

Lesson 2 Magnetic Field

Magnetic Field from a Wire What is the direction of the magnetic field created by the current flowing down through this wire? A. B. C. D. E. F.

Magnetic Field from a Wire What is the direction of the magnetic field created by the current flowing down through this wire? A. B. C. D.

Magnetic Field created by loop of wire What is the direction of the magnetic field at point P inside the loop of wire that is created by current flowing through it in the direction illustrated? A. ⃝ B. ⃝ C. D. E. None of these P

Magnetic Field created by loop of wire Which produces a stronger magnetic field at point P, if the current is the same and radius of the loop (R) is the same as the distance away from the wire (r)? Loop Straight wire The same Can’t be determined P

Magnetic Field created by a loop of wire You are looking a wire loop from above. Which way is the current flowing through the wire loop to create this magnetic field? To the right To the left Either to the right or the left; it doesn’t matter None of these I don’t know

Solenoid of Wire with Current If an iron bar was placed inside of this solenoid, which side would be the North pole Right Left Can’t be determined Both Neither

Magnetic Field in a Solenoid What is the direction of the magnetic field created by current flowing this solenoid? A. B. C. D.

Electromagnet Which way would the current need to be flowing in order to make the top end of the iron bar the North pole of the electromagnet? top wire  bottom wire  top wire  bottom wire C. Can’t be determined D. Don’t know

Electromagnet N S Which way would the current need to be flowing in order to make this electromagnet repel this permanent magnet? A. top wire  bottom wire  top wire  bottom wire C. Can’t be determined D. Don’t know

Magnetic Force on moving charged particles Lesson 3 Magnetic Force on moving charged particles

Examples using RHR #2

A proton is at rest at point P A proton is at rest at point P. The direction of the magnetic force on the proton is best represented by: A. B. C. D. E. None of these Choice One Choice Two Choice Three Choice Four Choice Five Choice Six P

Examples using RHR #2 A. B. C. D. E. F. G. None H. Can’t be determined

Examples using RHR #2 A. B. C. D. E. F. G. None H. Can’t be determined

Example Problem A particle with a charge of -33μC moves at 2,000 m/s at 40⁰ through a 6.5 T magnetic field. What is the direction of the magnetic force on the charged particle? A B C D E F G. None H. Can’t be determined

Electric Motor How will this loop of wire move if there is a current that flows around the loop as illustrated? A. B. C. D. E. F. None of these

Electromagnetic Induction Lesson 4 Electromagnetic Induction

Simple Model of a Generator Which way will the current flow through the conductor as the conductor moves down?   No current Can’t be determined

Simple Model of a Generator Which way will the current flow through the conductor as the conductor moves up along the metal bars?   No current Can’t be determined

Simple Model of a Generator Which way will the magnetic force act on the electrons in the conductor as the conductor moves down along the metal bars?   ↑ ↓

Simple Model of a Generator Which way will the magnetic force act on the conductor in the conductor as the conductor moves down along the metal bars?   ↑ ↓

Outlets What kind of current comes out of outlets in the United States? AC DC Both simultaneously Depends on the appliance you plug in

Electric Company What is coming from the electric company when we turn on a lamp in your bedroom? Energy Electrons Both Neither

Motor vs Generator If you had an electric motor, could you use it to make a generator, by spinning it create electricity? Yes All the parts are there, but you would have to rearrange them differently before it could work. No, that’s absurd I don’t know

Electromagnetic Devices Which device does a microphone function because of the same foundational fact? In other words, which device is the most similar in its functionality compared to a microphone? Speaker Generator Motor Two of these All of these

Transformers

Transformers Is it possible to cause current to flow in the secondary coil by turning the current in the primary coil on and off in this arrangement? (there is no physical connection between the two coils) Yes No Seems like a trick question, so yes

Transformers When is a voltage induced in the secondary coil of wire when the primary coil is connected to a battery? Right when the primary coil is turned on. While the primary coil has a steady current flowing through it (when it is left on). Right when the primary coil is turned off. A & B A & C

Transformer Why do transformers use alternating current? Because that is the most common type of electricity…made from generators. Because DC would get too hot. Because the electrons don’t actually get transported, they just vibrate back and forth. Because it creates a magnetic field in the coils that is constantly changing. None of these

Transformer What would happen if a transformer had a wooden core instead of an iron core? It wouldn’t work…impossible It would work, just not near as well It would work just a well as an iron core Depends on the type of wood

Transformer Your cell phone runs off of a 6V battery. When you charge your phone at night, what is the black box you plug into the outlet? Step-up transformer Step-down transformer Step-up and an Inverter (changes AC to DC) Step-down and an Inverter (changes AC to DC)

Transformer What kind of transformer is this? Step-Up Step-Down Both Neither Can’t be determined

Transformer In step-up transformer, what happens from the primary coil compared to the secondary coil? Voltage increases, Power increases Voltage increases, Power decreases Voltage increases, Power remains the same Voltage remains the same, Power increases Voltage decreases, Power increases

Transformer In step-up transformer, what happens to the current from the primary coil compared to the secondary coil? Current increases Current decreases Current remains the same

Transformer So in a step-up transformer the voltage in the secondary coil increases, and the current decreases. What must be true about the resistance of the secondary coil compared to the primary coil, based on Ohm’s Law (ΔV=IR) Resistance must be more Resistance must be less Resistance must remain constant Can’t be determined

Transformer In step-down transformer, what happens from the primary coil compared to the secondary coil? Voltage decreases, Current increases Voltage decreases, Current decreases Voltage decreases, Current remains the same Voltage remains the same, Current decreases Voltage increases, Current decreases

Transformer Which would be the correct expression of ratios for the relationship between voltage (ΔV), number of loops (N), and current (I) from the primary1 and secondary2 coils? A. ∆ 𝑉 1 ∆ 𝑉 2 = 𝑁 1 𝑁 2 = 𝐼 1 𝐼 2 B. ∆ 𝑉 1 ∆ 𝑉 2 = 𝑁 1 𝑁 2 = 𝐼 2 𝐼 1 C. ∆ 𝑉 1 ∆ 𝑉 2 = 𝑁 2 𝑁 1 = 𝐼 1 𝐼 2 D. ∆ 𝑉 1 ∆ 𝑉 2 = 𝑁 2 𝑁 1 = 𝐼 2 𝐼 1

Transformer Which will dissipate less Power across power-lines, based off of this equation P=I2R? High current Low current Which transformer causes this? Step-up Step-down