SLK Q2W1 General Physics 2 PDF

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Republic of the PhilippinesDEPARTMENT OF EDUCATIONRegion IDivision of Ilocos SurSELF LEARNING KIT INSHSGENERAL PHYSICS 2MAGNETISM&LORENTZ FORCE; MOTION OFCHARGEDPARTICLES IN ELECTRIC ANDMAGNETIC FIELDS; MAGNETIC FORCESON CURRENT -CARRYING WIRESActivity 1: Magnet Word Search: Encircle the words t...

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Republic of the Philippines

DEPARTMENT OF EDUCATION Region I Division of Ilocos Sur

SELF LEARNING KIT IN

GENERAL PHY PHYSICS SICS 2

SHS

MA MAGNETISM GNETISM & LORENTZ FOR FORCE; CE; MO MOTION TION OF CHAR CHARGED GED PART ARTICLES ICLES IN ELECTRIC AND MA MAGNETIC GNETIC FIELDS; MAGNETIC FORCES ON CURRENT -CARRYING WIRES

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Perhaps you have picked up paper clips, pins, or tacks with a magnet or made an electromagnet by coiling a piece of wire around a nail and connecting it to a dry cell. In the activity below, try to recall the terms associated to magnetism.

Activity 1: Magnet Word Search: Encircle the words that are indicated below. The answers can be diagonal or reverse. MAGNET FARADAY F D O L S C G M

A U L O A A O A

R C D D F L M G

MAGNETIC FIELD MAGNETISM A K E E B S A N

D Y G S O E G E

A A O T N T N T

Y D D O E G E I

POLES LODESTONE L A W N T H T C

R R G E F A I F

A A D I B S S I

TESLA WEBER M F A S T E M E

E G S A T L R L

P O L E S L O D

Magnetism is used is used in common fixtures, advanced technologies, research, and even in medicine. It is utilized in magnetic memo holders, doors, motor in refrigerator, speakers, motor in a washing machine, MRI (magnetic resonance, and magnetically levitated trains.

MAGNETISM Magnetism is considered as the first cousin of electricity for they are much related t each other. Electromagnetism is the part of physics that deals with relationship between electricity and magnetism. The origin of electricity and magnetism sprang from ancient men’s curiosity over the ability of two materials amber (original word for electricity) and lodestone to attract other materials. Magnetism is the term used to refer to the ability of lodestone to attract iron. A 2

material having this property is called a magnet. The modern name for lodestone or magnetic iron core is magnetite. Lodestone literally means ‘way-finding stone’. When suspended freely, one end of a lodestone always points north and the other end points south. This suspended lodestone is the first compass. The Chinese were making use of it as a navigational tool in the eleventh century. CLASSIFICATION OF MAGNETS Magnets may be natural or artificial. Natural magnets are found in nature and are called lodestones or magnetites. Humans use a magnetic substance to make artificial magnets. A magnetic substance is one that is attracted by a magnet and can be magnetized. Examples of magnetic materials are iron, steel, and cobalt. Nonmagnetic materials are not attracted by magnets and cannot be made into magnets. Examples are wood, paper and glass. A piece of iron or magnetic material can be magnetized in three ways: a) stroking it with permanent magnet, b) through electric current, and c) through induction from Earth’s magnetism.. Artificial magnets may be temporary or permanent. Retentivity is the ability of a magnetic material to retain its magnetism after it has been magnetized. Steel has high retentivity, whereas pure iron is an example of a temporary magnet. MAGNETIC POLES A magnet has polarity. It has two ends called magnetic poles. The end that points northward is the north pole and the end that points southward is the south pole. Magnets attract or repel without touching one another just as electrical charges do. The strength of the repulsion and attraction depends on the distance between the magnets. The law of magnetic poles states that like magnetic poles repel each other while unlike magnetic poles attract each other. Magnetic poles and electric charges behave similarly in some ways. However, take note of the very important difference. Electric charges can be isolated while magnetic poles cannot. A group of electrons need to be accompanied by a cluster of protons. On the other hand, a north pole never exists without presence of a south pole.If you break a bar magnet in a half, each half still behaves as a complete magnet (Figure 1). Break these in half and you have 4 magnets, each with a north and a south pole. Keep breaking the pieces further, there are still two poles. Magnetic poles exist in pairs.

Figure1: Breaking a Bar Magnet http://elementsofelectricalengineering.blogspot.com 3

MAGNETIC FIELD A magnetic field βis a region of space where a magnet is capable of exerting a force on a magnetic material. It is where the magnetic force acts. Consider a current- carrying wire passing through a magnetic field at right angles to the wire. Experimental results show that the force F on the wire is proportional factors, namely, the magnetic field strength β ,the current I in the wire, and the length L of the wire that lies in the magnetic field. It is expressed as F= β I L The force, current, and length can be measured, hence, the magnetic field strength can be calculated using the equation β=

F IL

The shape of the field is revealed by magnetic field lines (Figure 2).

Figure2: Magnetic Field Lines https://physics.stackexchange.com

The unit of Βis Tesla (T), where: 1 tesla = 1

Newton Ampere −meter

=1

weber 2 meter

1 gauss= 10-4 T The magnetic fields of a straight wire, a loop, and a solenoid, where moving charges exist, are given. Each is given the value of β at the indicated point A. You assumed that surrounding material is vacuum. The constant µo= 1.257 x 10-6 T m/A is the permeability of free space. 1. Magnetic Field of a straight, currentcarrying wire (Figure 3) β=

µo I 2π s

where: µo= magnetic permeability of free space s= distance to point A from axis of 4

Figure3: Magnetic Field of a straight, current-carrying wire https://phys.libretexts.org

the wire I= current Direction of β: Grasp the wire with your right hand. The thumb points in the direction of the current, the curled fingers of that hand point in the direction of β. 2. Magnetic field of current-carrying wire loop (Figure 4)

β=

µ o∋ ¿ 2r ¿

where: r= radius of the loop N= number of turns I= current 3. Current-carrying solenoid (Figure 5) Solenoid is the generic term for a coil of wire used as an electromagnet. β=

Figure4: Magnetic Field of a straight, current-carrying wire loop http://hyperphysics.phy-astr.gsu.edu

µ o∋ ¿ L ¿

where: N= number of turns L= length of the solenoid I= current Figure 5: Current-carrying solenoid https://www.miniphysics.com

MAGNETIC FLUX

Magnetic flux is defined as the product of the area of the surface swept out by the moving conductor and component of the magnetic field B that is perpendicular to this area. In symbols Φ = BA cos ɸ where: B= magnetic field strength A= area ɸ = angle between the magnetic field and a line perpendicular to the area ELECTRIC FIELD VS. MAGNETIC FIELD An object with a moving charge always has both magnetic and electric field. They have some similarities and has two different fields with same characteristics. Both fields are interrelated called electromagnetic field but there are not depending on each other.

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Figure6: Electric Field vs. Magnetic Field https://byjus.com/

The difference between electric field and magnetic field is summarized in the table below.

Difference Between Electric Field vs. Magnetic Field Electric Fields Magnetic Fields It creates an electric charge in surrounding Creates an electric charge around moving magnets Measured as newton per coulomb, volt per Measured as gauss or tesla meter Proportional for the electric charge Proportional to the speed of electric charge Are perpendicular to the magnetic field Are perpendicular to the electric field

To further enhance your understanding on magnetism. Read and understand the sample problems indicated below.

Sample Problem 1: A wire 0.20 m long carries a current of 6 A. The wire is at right angles to a uniform magnetic field. The force on the wire is 0.40 N. What is the magnitude of the magnetic field? Solution: Given: L = 0.20 m β=

I= 6 A

F = IL

F= 0.40 N

0,40 N = 0.33 6 A (0.20 m)

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N Am

Find: β = 0.33 T

Sample Problem 2: A wire 0.50 m long carrying a current of 8 A is at right angles to a 0.40 T magnetic field. How strong a force acts on the wire? Solution: Given: L= 0.50 m

I= 8 A

β= 0.40 T

Find: β

F= βIL = (0.40 T)(8A) (0.50 m) = 1.6 N Sample Problem 3: A closely wound, flat, circular coil of 40 turns of wire has a diameter of 12 cm and carries a current of 2 A. Determine the value of β at its center. Solution: Given: N= 40

d= 12 cm

µo∋ ¿ β= 2r = ¿

I= 2 A

Find: β

m ( 0.40 N )(2 A ) A =8. 38x10-4T 2(0.06 m)

1.257 x 10−6 T

Sample Problem 4: A solenoid with 3 000 hoops is 60 cm long and has a diameter of 1.5 cm. If the magnetic field within it is 3.771 x 10 -2 T, find the current that is sent through the wire. Solution: Given: N= 3000 Find: I

L= 60 cm

β=

µo∋ ¿ 2r ¿

I=

βL µoN

=

d= 1.5 cm

3.771 x 10−2 T (0.6 m) 1.257 x 10−4 T m/ A(3000)

β= 3.771 x 10-2 T

= 6.0 A

Sample Problem 5: The vertical component of the Earth’s magnetic field in a certain region is 2.5 x 10 -5 T. What is the potential difference between the rear wheels of a car, which are 4 ft apart, when the speed of the car is 50 mi/h? Solution: Given: β= 2.5 x 10-5 T l= 4ft I= 4ft x v= 50

v= 50 mi/h

0.305m = 1.22 m 1 ft mi 1.609 km 1000 m x x h 1 mi 1 km

Find: Ve

x

1h 3 600 s

= 22.35 m/s

Ve = βIV = 2.5 x 10-5 T (1.22 m) (22.35 m/s) = 6.82 x 10-4 V

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Congratulations! You are done with this Self Learning Kit. Try to assess yourselves by doing the following exercises/ activities. Follow the directions carefully. God bless you! Activity 2: Understanding Right Hand Rule Analyze the following items; Underline the correct answer in the parenthesis. 1. A current runs through a wire such that it generates a magnetic field. The magnetic field is in the clockwise direction in the plane of your computer or cellular phone screen. What is the direction of the current? (Counter-clockwise, Into the screen, Clockwise, Out of the screen) 2. A current runs through a straight wire from right to left. What direction would the magnetic field be? (Left to right, Out of the screen, Right to left, Counter-clockwise Into the screen) 3. A straight wire carries a current directly into your computer/cellular phone screen. In what direction would the magnetic field be? (Right to left, Clockwise, Counter-clockwise, Out of the screen, Into the screen) 4. A straight wire carries a current directly out of your computer/cellular phone screen. In what direction would the magnetic field be? (Out of the screen, Left to right, Clockwise, Into the screen, Counter-clockwise) 5. A negatively charged particle is moving to the right along a vertical plane. If the force generated by a constant magnetic field is directed upwards within plane, in what direction is the magnetic field? (Out of the plane, toward the observer; Upward within the plane; Out of the plane, away from the observer; Downwards within the plane) Activity 3: Solving Magnetism Solve each problem. Show your complete solution. 1. A wire 85 cm long carries a current of 5A and is at right angles to a uniform magnetic field. The magnitude of the wire is 1.0 N. What is the strength of the magnetic field? 2. A solenoid 60 cm long has 5 000 loops around it. Compute β when a current of 0.50 A passes through in the winding. 3. What current would have to be maintained in a circular coil of wire of 50 turns and 3 cm radius in order to cancel the effect of the Earth’s magnetic field at a place where the horizontal component of the Earth’s field has an induction of 2 x10 -5 Wb/m2? 4. Compute the flux density in air at a point 8 cm from a long straight wire carrying a current of 7 A.

In this section, it is expected that you differentiate electric interactions from magnetic interactions and evaluate the total magnetic flux through an open surface. The following salient concepts of this lesson are listed below.

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Summary:    

Magnetic field is a region of space where a magnet is capable of exerting a force on a magnetic material. It is where the magnetic force acts. The unit of magnetic field is Tesla (T) Electromagnetic induction happens when voltage is induced by changing the magnetic field around a conductor. Magnetic flux is defined as the product of the area of the surface swept out by the moving conductor and component of the magnetic field B that is perpendicular to this area

In this lesson, we learn that electricity and magnetism are “cousins”. Electromagnetic motors are a big part of everyday life, as well as industries and factories. We may not even realize that we interact with electromagnets on a daily basis as we use a wide variety of motors to make our lives easier. In this activity, you will create a simple electromagnet and try to investigate ways to change the strength of an electromagnet.

Activity 4: Building an Electromagnet Materials: 1 nail, 2 feet (.6 m) of insulated wire, 1 D-cell battery, several paperclips (or tacks or pins) and a rubber band Procedure: 1. Wrap the wire around a nail at least 20 times (see Figure 7). Wrap your nails tightly, leaving no gaps between the wires and not overlapping the wraps. 2. To continue making the electromagnet, connect the ends of the coiled wire to each end of the battery using Figure7: Electromagnet Setup the rubber band to hold the wires in place. https://www.teachengineering.org 3. Test the strength of the electromagnet by seeing how ma 4. Fill in the table below with how many paper clips your electromagnet was able to pick up. 5. Electromagnet

How Many Paperclips Did It Pick Up?

With 20 coils With fewer coils How many coils: ________ With more coils 9

How many coils: ________ Observation: 1. Write a sentence about how changing the number of coils affects how many paper clips the electromagnet could pick up. ______________________________________________________________________ ______________________________________________________________________ 2. Can the electromagnet pick up paperclips when the current is disconnected? Why? ______________________________________________________________________ ______________________________________________________________________ 3. Aside from changing the number of coils. What will you do to modify in your electromagnet? ______________________________________________________________________ ______________________________________________________________________ Rubrics for Laboratory Activity CATEGORY Observations (one per question) Recognition

Organization

3 Observations were very detailed and correct Clearly recognizes of relevant information necessary to solve problem Contents are well organized

2 Observations were correct but not detailed Somewhat recognizes relevant information to solve problems Contents are fairly organized

1 Observations were not correct and not detailed Little to no recognition of relevant information necessary to solve problem Contents are somewhat well organized

Multiple Choice: Write the letter of the correct answer on the space provided before the number. _____ 1. The unit of tesla is equivalent to ___________. A. N-A/m C. N/A-m B. A-m/N D. N-A/m _____ 2. The force on a current-carrying wire is proportional to the following quantities EXCEPT A. cross-sectional area C. length B. current D. magnetic field strength _____ 3. When the ends of two bar magnets are near each other, they repel. The ends must be A. one north, the other south C. one south, the other north B. both south D. one north, one east _____ 4. A faster motion between the conductor and magnetic field induces ____________. A. greater current C. lesser voltage B. greater voltage D. lesser current

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_____ 5. A straight wire parallel to the ground carries a steady current to the west. At a point directly below the wire, what is the direction of the magnetic field that the wire produces? A. south B. north C. east D. west _____ 6. Which of the following characteristic/s is/are related to magnetic fields? I. Measured as newton per coulomb, volt per meter II. They create an electric charge in surrounding III. They are proportional to the speed of electric charge A. I and II B. I and III C. II only D. III only _____ 7. If you are looking directly into one end of a long solenoid, the magnetic field at its center points at you. What is the direction of the current in the solenoid? A. clockwise C. directly towards you B. counter clockwise D. directly away from you _____ 8. A wire 30 cm long carrying a 6 A is at right angle to a 0.40 T magnetic field. How strong a force acts on the wire? A. 0.72 N B. 4.5 N C. 72 N D. 450 N _____ 9. A circular coil has 50 turns of wire has a diameter of 13 cm and carries a current of 3 A. What is the magnitude of the magnetic field? A. 2.89 x 10-6 T C. 2.89 x 10-3 T -6 B. 1.45 x 10 T D. 1.45 x 10-3 T _____ 10. A wire is at right angle to a uniform magnetic field has a force of 0.50 N and carries a current of 6 A. How long is the wire with if the magnitude of magnetic field is 0.35 T? A. 0.12 m B. 0.24 m C. 1.1 m D. 34 m

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LORENTZ FORCE; MOTION OF CHARGED PARTICLES IN ELECTRIC AND MAGNETIC FIELDS; MAGNETIC FORCES ON CURRENT -CARRYING WIRES

There is a way to confine electrons and make them move in a circular motion without spatial restrictions of their paths. Before you go further in this lesson, perform the “Water Bucket Go Around” activity and answer the preceding questions.

Activity 1: Water Bucket Go Round! Materials: Styrofoam /plastic cup, water, string Procedure: 1. Attached the string to the Styrofoam cup with water. Move to an area in the room where you have space to swing the “water bucket” in a circular motion without hitting someone. Do some trials. 2. Observe the motion of the “water bucket” as you swing it in a circular motion. Draw a diagram of the “water bucket” and its path

Answer the following questions: 1. What kind of force in classical physics is most closely related to the motion of electrons (represented by water) as shown by your drawing above, if the electrons as assumed as classical mass particles? _____________________________________________________________________ 2. The equation below is one of the equations in circular motion: FC = mac =

m

v2 r

What is the property of electrons that determines the radius of their circular motion? 12

_________________________________________________________________

There is a way to confine electrons and make them move in a circular motion without spatial restrictions of their paths as shown by the activity above where you simulate how electrons are confined to move within a circular path. Electric force has a charge interaction where stationary/moving charges are both affected. On the other hand, in magnetic force has a charge interaction of a moving charge, whose velocity has a component that is perpendicular to the magnetic field vector, interacts with magnetic field.

CYLOTRON The cyclotron was one of the earliest types of particle accelerators, and is still used as the first stage of some large multi-stage particle accelerators. It makes use of the magnetic force on a moving charge to bend moving charges into a semicircular path between accelerations by an applied electric f...