# Grade 12 Physics Independent Study

**Grade 12 Physics Independent Study**

**Nelson 12 Textbook**

Instructions:

- Every Grade 12 physics student is responsible for learning several topics on his/her own, much like university. This independent study gives the student an opportunity to learn how to learn on their own. The main reference textbook is Nelson12 Physics, however, there are other high school reference books at school or public libraries that can be of help.
- Do the suggested reading in the following pages along with the questions and problems indicated.
- As you read and do the questions, make notes and summaries on definitions, concepts and formulas. Answer non-numerical questions as well. Put these in one notebook. In another notebook, write out solutions for the problems assigned in GUFSA format.
- At the end of November and early December, the teacher will interview with each student on their progress. At this time, students must show the teacher their notebooks and work to date. The notebooks are not marked, but it is strongly advised that students make two good notebooks to do well on the culminating exam.
- Students must also set up an eight inch by eleven inch aid sheet on both sides that summarize all the key formulas, concepts and definitions studied. This aid sheet can be used on a culminating exam worth 10% of the final mark in the course. The culminating exam will occur roughly on the third week of January with a fixed date determined in late December.
- If students are having difficulties with any of the ISU work, they are welcome to come in and get extra help with the teacher at lunch or after school.
- The ISU material will not be covered on the final exam. The final exam just covers material learned in class during teacher presentations.

Page #1

**Electric Fields:**

- Read p320 to321 What subatomic particles are the basic units of charge? What is the law of electric charges? What does +e and -e stand for? P320 If an object has equal numbers of protons and electrons, what is its total charge? If an object has too many or an excess of electrons to balance the #protons, what type is its charge? If an object has too few or a deficit of electrons to balance the #protons, what type is its charge? What is law of conservation of charge? P321 What is the SI unit of electrical charge? What is the charge on the electron and proton in terms of Coulombs? Do you think an object can have a net charge of -3/4e ? Why or why not? Why does the alpha particle or Helium nucleus have a charge of 3.20 X 10-19 C? P321
- Read from middle of p321-326. Define: conductor, insulator Contrast placing charge on an insulator compared to placing a charge on a conductor like a metal. Briefly explain how to charge an object a) by friction b) by contact

c) by induced charge separation d) by induction via grounding Do Q1,Q5 p326 check ans p719

- Read p327 to p332 Define: electric force What is Coulomb's Law? Memorize it. What is the equation for Coulomb's law? Memorize it. What does each symbol in Coulomb's equation stand for? What is Coulomb's constant in the SI system? Note well: Coulomb's equation only gives us the magnitude of the electric force, so don't substitute negative signs for charge into the formula. Even though force is a vector, Coulomb's formula is a scalar equation. After the calculation, use the law of charges to figure out the direction of the electric force. If there are two or more other charges, find the individual magnitudes of the electric forces, find the direction of the electric forces as prescribed, then use vector addition rules to find the net force acting. What principle is this? See p329 How is Coulomb's law similar and different from Newton's law of universal gravitation? See p328 Review tutorial #1, sample problem #1,#2, #3 p330-332 Solve Q1 to Q3 p332Check answers same page Solve Q1 to Q10 p333 Check answers p719 p373 Q55-Q57 Q59-Q65
- Read p334 to344 An electric field can be loosely described as a region of space where an electric force is exerted on charges. Briefly describe how electric fields create images on LCD displays. P334 Fill in the blanks: The more precise definition of the electric field is electric force per unit ______charge with an SI unit of ______. see p334 There are two equations for electric field, one is a vector equation and one is a scalar equation that can be used to determine the magnitude of the electric field due to a point charge. Memorize these formulas and be able to derive the scalar equation. Be sure you know what the symbols stand for. See pages 334 - 335
**Note again well:**the scalar equation only gives us the magnitude of the electric field due to a point charge, so don't substitute negative signs for charge into the formula. Even though electric field is a vector, this is a scalar equation. After the calculation, figure out the direction of the electric force on a positive test charge at this point in space using the law of charges depending on whether the nearby point charge is negative or positive. If there are two or more other point charges, find the individual magnitudes of the electric fields on a positive test charge, determine the direction as prescribed, then use vector addition rules to find the net electric field acting. Review tutorial #1, sample problems #1 and #2 then try Q1-Q3 p337check answers same page - Read p338-341The electric field at any point in space near a point charge can be represented by electric field lines. Fill in the blanks: The direction of electric field lines tells us the direction of the electric force on a ______test charge. The ______of the field lines is proportional to the magnitude of the electric field. A positive point charge transmits an electric field directed radially ______. A negative point charge transmits an electric field directed radially ______. The magnitude of the electric field is inversely proportional to the ______of the distance from the charge. Define electric dipole. Sketch the electric field lines near a) a positive point charge b) a negative point charge c) an electric dipole d) two identical charges near each other. Can you explain these electric field line patterns? The book fails to mention how the direction of the electric field can be determined from a curved electric field line pattern. By drawing a tangent line to the curved electric field line at a point in space, we can determine the direction of the electric field and therefore the direction of the electric force on a positive test charge placed at that point. Read over p341 What set up can create a uniform or constant electric field? Sketch and briefly describe the electric field line pattern between and near the edges of this set up. What is the electric field magnitude outside of this oppositely charged parallel plate set up? What does the constant electric field between parallel plates depend on?
- Read over p342 – p344 What is the purpose of an electrostatic precipitator? Use a diagram to describe how it works. Compare the magnitude of the earth's electric field on a clear day with the minimum magnitude of the electric field emitted by the prey of the electric field-detecting hammerhead shark.
- Solve Q1,2,3,4,6,7 p345check answers p719P373 Q67, Q68, Q69, Q 70 , Q71, Q72, Q73check answers p719
- Read p346 -p347 BUT there are a few errors and clarifications. The title on the bottom of p346 should read “Work and Electric Potential Energy” . Define and know electric potential energy. This section deals with a constant non-zero electric field, like between oppositely charged parallel plates. If we place a charge at rest in that electric field,

page #2

the electric field is able to do work on that charge. We say the electric field has electric potential energy. As work is done on the charge, the electric field's potential energy decreases i.e W = -ΔEE or ΔEE = -W The book is dealing with displacements parallel to the electric force or electric field, so the book uses a short cut equation for work,

W = FE Δd so ΔEE = -W = - FE Δd = -q E Δd Memorize this, but you should know that electric potential

energy is a scalar even though we substitute for vectors in this equation. Also realize the vectors involved are collinear and therefore we can represent them as integers. For instance, if an electron is placed at rest in an

electric field, the electron will move in the opposite direction of the electric field or the electric force, (remember the electric field points in the direction of the electric force on a positive test charge) positive work is done and there is an electric potential energy loss. So when you substitute into the equation ΔEE = -q E Δd , if the electric field is in a positive direction, the displacement must be negative, and in this case we must substitute the sign of the charge which is negative. Overall a negative X negative X negative yields a negative, or a loss in electric potential energy. Remember signs are important in vector equations. In general and in the absence of applied or frictional forces, if the electric potential energy decreases the kinetic energy increases and vice-versa so that mechanical energy is conserved. In equation form ΔEk = -ΔEE or mv22/2 - mv12/2 = +q E Δd . Memorize and know this. Use these equations to review and redo tutorial #1and the sample problems, then do Q1,Q2, Q3 p349 Ans on pg

- Read p350 to p353
- Define and know: electric potential definition in words, electric potential defining equation and SI unit, equivalent electric potential units in terms of Joules and Newtons. If we double the charge in a constant or uniform electric field, how does the electric potential energy and electric potential change? Define and know: electric potential difference definition in words, electric potential difference defining equation and SI unit. In a uniform or constant electric field such as between a parallel plate apparatus, derive the equation ΔV = - E Δd . Keep in mind the book did not emphasize that E and Δd are vectors. Know it. If there is no change in electric potential for a very small change in displacement, what is the electric field strength over that displacement? Fill in the blanks: positive charges move naturally from ______potential to______potential. Electrons move naturally from ______potential to ______potential. In a uniform electric field without friction or applied forces, keep in mind ΔEk = -ΔEE or mv22/2 - mv12/2 = +q E Δd as before, but

ΔV = - E Δd so mv22/2 - mv12/2 = - q ΔV Memorize this. Review and redo sample problems #1 and #2 on p352 and 353. Do practice p353 Q1,2,3 Check answers on the same page. Do Q1 to Q10 on p354. Check answers p719

- Read p355 to p361
- What is the defining equation for the electric potential due to a point charge? Memorize. At an infinite distance from a point charge, what is the value of the electric potential? What is the defining equation for the electric potential energy due to two charges near each other. Memorize. When two charges are separated by an infinite distance, what is the value of the electric potential? Learn how to calculate electric potential and electric potential energies due to point charges by reviewing and redoing sample problems p357 to p360, then do q1 to q4 on p360 check answers on same page. Do questions 1, 4 to 7 p361 check answers p719
- Read p362 to p365
- What is the main conclusion from Millikan's oil drop experiment? What is meant by elementary charge and fundamental physical constants? What is the charge in Coulombs for the electron and proton? Can we have a charge equal to 1/4 of an elementary charge? Derive Millikan's equation q = mgd/ΔV. What do the symbols in

q = Ne stand for? How does the equation help us? Learn how to use these equations in Millikan problems by reviewing and redoing sample problems p363-p364 then do Q1 to Q3 p364 Check answers same page then do Q1 to Q7 p365 check answers p719

- Do p373 Q74 to 76, Q78, Q80 to Q90 Check answers p719

**Now try these review problems:**

- What is the electrical force between charges of 50.0 nC and 100.0 nC if they are 5.00 cm apart? (Ans 0.0182 N repulsive)
- Two charges exert an electrical force of “K” Newtons on each other. If one charge is doubled, the other charge is divided by three, and the distance is multiplied by four, what is the magnitude of the new electrical force? (ANS (1/24) K N)
- Two identical positive charges of magnitude +2.0 C are 16 cm apart. A third charge of +3.0 C is on the right bisector of the first two charges with the angles 36.9° as shown. Find the size of the net electrical force on the 3.0 C charge? ( Ans 6.5 X 1012 N)

page #3

- The electric field strength is 4.0 N/C [E]. What is the electrical force on a charge of -5.0 C charge in this field? (Ans 20 N [W])
- A -6.0 C charge experiences a 30.0 N [W] electrical force. What is the electric field strength? ( Ans 5.0 N/C [E])
- A +2.0 C charge is 20 cm to the right of a -3.0 c charge. What is the electric field on the line exactly halfway between the two charges? (Ans 4.5 X 1012 N/C [Left] )
- Millikan's experiment determined that all charge is an integral multiple of the elementary charge. What is the value of the elementary charge? If a neutral atom gains 3 electrons, what is its charge? (Ans 1.6 X 10-19C, 4.8 X 10-19 C )
- It takes 4.2 X 10-3 J of energy to move a 1.2 X 10-6 C of charge against an electric field from one point to another. What is the magnitude of the potential difference between the two points? ( Ans 3500 J/C or 3500 V)
- Parallel plates are 5.0 mm apart and have a potential difference of 300 Volts between them. If a +2.0 C charge is between the plates, what is the magnitude of the electrical force on the charge? ( Ans 1.2 X 105 N)
- In a Millikan-type experiment, two horizontal parallel plates are 2.5 cm apart. An oil drop of mass 1.5 X 10-15 kg remains at rest when the potential difference between the plates is 460 V with the upper plate positive. How many excess or deficit electrons does the drop have? (Ans 5 excess electrons)
- An alpha particle of +2 elementary charges and mass 6.7 X 10-27 kg can be given some speed by placing it at rest on the positive side of a 2000 Volt parallel plate apparatus. Ignoring any gravitational effects, what speed does the particle have when it reaches the negative plate? (Ans 4.4 x 105 m/s)

**Magnetic Fields:**

- Read p376 What does MRI stand for? What do MRI devices use to make very strong magnetic fields around the human body? What is the medical use of the MRI?

Read p378 – p382 In your own words, summarize how the northern lights (aurora borealis) and southern lights (aurora australis) occur? Note that B is the symbol for magnetic field and is a vector, but magnetic field is not the same as magnetic force Fmag **Fill in the blanks:** Iron filings around a bar magnet show the ______

______. Similar to the law of charges and electrical force, like poles ______each other and unlike poles ______each other. Unlike electric fields that can result from single charges, magnetic fields will always result from a magnetic ______. Unlike charges and electrical forces, you can never have only a ______pole or only a ______pole. Magnetic field lines move ______from the north pole and ______toward the south pole. See p379 Draw magnetic field lines around a a bar magnet. How does the shape of the magnetic field around a magnetic dipole compare with the shape of the electric field around a charge dipole? See Fig 3 p379 Fill in the blanks: Magnetic field lines always form ______loops. Inside a magnet, the field lines go from the ______pole to the ______pole. Top p380 Sketch the magnetic field lines inside and outside a horseshoe magnet. Look back to Fig 3 p379. Note the direction of the magnetic field B is along the tangent line to the curved magnetic field lines. This direction is the same direction that the north pole of a compass needle points. The density or number of field lines increases near the poles. Note also that magnetic field lines, like electric field lines, never cross. Fill in the blanks: The earth's core acts like a giant ______magnet. The earth's north geographic pole is actually a ______magnetic pole, however, it is conventional to call it otherwise. Last few sentences p380 What happens to the polarity and position of the earth's magnetic poles over time? P381 top A magnetic field produces a magnetic force on a moving charged particle that is ______to both the direction of the magnetic field and the particle's velocity. Top p382 Use this fact to explain how cosmic rays, fast moving charged particles from the sun and stars, get deflected at the equator by the earth's magnetic field but spiral around magnetic field lines near the magnetic poles of the earth. Explain why a magnetic field can never speed up a moving charged particle. P381-382

- Read p382 – p385 State Oersted's 1820 “principle of electromagnetism” and know it. The direction of current used in this course an in this textbook is called “conventional current”, which is the flow of positive charge from the positive terminal to the negative terminal. Compare conventional current with tha actual flow of electrons in a circuit. See sidebar p382 Sketch the magnetic field around a straight wire conducting current. State and memorize the right-hand rule for a straight conductor. P382 Sketch the magnetic field of a looped wire carrying current. Indicate the direction of conventional current in your diagram. P383 Define and know what a solenoid is. Sketch the magnetic field inside and outside of a solenoid carrying current. State and memorize the right-hand rule for a solenoid. Fill in the blanks: Applying a current through a solenoid causes the solenoid to become an ______. Turning the current on or off allows us to control the ______. p384

State two ways we can increase the strength of an electromagnet. State four uses of electromagnets. P384

- Read p386 – p389 what is the SI unit of magnetic field strength. How can this derived unit be expressed in terms of other SI metric units. Top p386 Compare the magnetic field strength of a fridge magnet, the earth's amgnetic field, and a MRI unit. What happens to an electron beam (cathode ray) when a bar magnet is brought near? See

Page #4

Fig 2 p386 Whenever a charge moves through a magnetic field, the strength of the magnetic force on that charge depends on the size of the charge in Coulombs, the strength of the magnetic field in Tesla, and what else? To determine the size of the magnetic force on a charge moving through a magnetic field there is a scalar equation we can use with no directions or negatives required. State and memorize this equation and know what the symbols stand for. See top p387 To determine the direction of the magnetic force on a moving charge through a magnetic field, we use the right-hand rule for a moving charge in a magnetic field, or sometimes called the “Hi” or “palm rule”. State and memorize this rule. Be careful. This rule applies to positive charges. If the charge is negative, keep in mind the direction of the magnetic force will be in the opposite direction. P387 Review and redo sample problems on p388-p389 Do practice Q1-Q4 p390 check answers same page Do Q2-Q10 p391 check answers p719 Note X means “into the page” and ● means “out of the page”