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Physics Grade 12 Unit 4 Electromagnetism MCQs with explanation

PART 2

6. 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, as viewed by you?
A. clockwise
B. counterclockwise
C. directly toward you
D. directly away from you

Answer B. counterclockwise.
Explanation:
• To determine the direction of the current in a solenoid, you can use the right-hand rule.
• If you curl the fingers of your right hand in the direction of the current, your thumb will
point in the direction of the magnetic field inside the solenoid.

7. The number of turns in a solenoid is doubled, and its length is halved. How does its magnetic field change?
A. It triples.
B. It is halved.
C. It quadruples.
D. It doubles.

Answer C
𝐁 = 𝝁𝒐𝐈𝑵/𝒍

8. According to Faraday’s law of electromagnetic induction
A. Electric field is produced by time varying magnetic flux
B. Magnetic field is produced by time varying electric flux.
C. Magnetic field is associated with a moving charge.
D. None of the above

Answer A.
Explanation: Faraday’s Law of Electromagnetic Induction states that a time-varying magnetic flux through a loop of wire induces an electromotive force (emf) and, consequently, an electric field in the loop.
• This induced electric field is non-conservative and is created by the changing magnetic field.

9. The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a short galvanometer. The magnet was held stationary for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly. The maximum deflection of the galvanometer was observed when the magnet was
A. Moving towards the solenoid
B. Moving into the solenoid
C. At rest inside the solenoid
D. Moving out of the solenoid

Answer D.
Explanation:
• According to Faraday's Law of Induction, an electromotive force (EMF) is induced in
the solenoid when the magnetic flux through the solenoid changes.
• The maximum deflection of the galvanometer occurs when there is a rapid change in the
magnetic flux.
• The flux through the solenoid changes most rapidly when the magnet is moving out of the
solenoid because this movement causes the magnetic field to change quickly, inducing the maximum current in the solenoid

10. A bar magnet is divided in two pieces. Which of the following statements is true about the force between the broken pieces if they face each other with a small separation?
A. There is an electric repulsive force between the broken pieces.
B. There is an electric attractive force between the broken pieces.
C. There is a magnetic repulsive force between the broken pieces.
D. There is a magnetic attractive force between the broken pieces.

Answer D.
Explanation:
• When a bar magnet is broken into two pieces, each piece becomes a smaller magnet with its own north and south poles.
• These smaller magnets will attract each other because the opposite poles (north and south) of the broken pieces will face each other, creating a magnetic attractive force.
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Physics Grade 12 Unit 4 Electromagnetism MCQs with explanation

PART 1

1. A freely suspended bar magnet rest in:
A. North-South direction
B. East-west direction
C. North-East direction
D. South-East direction

Answer A
A freely suspended bar magnet always rests in North-south direction because the North pole of the magnet lies in the geographic North direction and the south pole of the magnet lies in the geographic south direction. So, it aligns itself in N-S direction. As unlike poles attract and like poles repel.

2. Which one of the following is not true about the motion of charged particle in a uniform magnetic
field?
A. Magnetic force changes only the direction of the charge and the speed of the particle stays
constant.
B. The force experienced by the charged particle is only the centripetal force
C. The force is zero when the particle moves along the field lines
D. The force does maximum work when the charge moves perpendicular to the magnetic field strength

Answer D.
The magnetic force on a charged particle always acts perpendicular to the particle's velocity, so it cannot do work (as work requires a force component in the direction of motion).

3. A charged particle is moving in a magnetic field. What is the direction of the force on the particle due to the magnetic field?
A. in the direction of the magnetic field
B. in the direction opposite to which the particle is moving
C. in the direction that is perpendicular to both the magnetic field and the velocity
D. in the same plane as the magnetic field and the velocity, but not in either of those two
directions

Answer C.
Explanation:
The force on a charged particle moving in a magnetic field is given by
𝐹 = 𝑞(𝑣𝐵⃗ ) The direction of the force is perpendicular to both the velocity of the particle and the magnetic field, as determined by the right-hand rule. This means the force is always at a right angle to both the direction of motion and the magnetic field.

4. An electron and a proton enter a magnetic field perpendicularly. Both have same kinetic energy.
Which of the following is true?
A. Trajectory of electron is less curved
B. Trajectory of proton is less curved
C. Both trajectories are equally curved
D. Both move on straight line path

Answer B. Trajectory of proton is less curved.

5. Magnetic fields can be pictorially represented by magnetic field lines, which one of the following is not true about the properties of these field lines?
A. The field is tangent to the magnetic field line.
B. Field strength is proportional to the line density.
C. Field lines can cross each other.
D. Field lines are continuous loops.

Answer C
Explanation
=> Magnetic field lines are cannot cross each other.
=> Form closed loops.
=> No beginning or end points; they are continuous.
=> The field strength is stronger where the lines are closer together
=> Direction is from the north pole to the south pole outside the magnet, and inside the magnet from south to north

Part 2 Continued.......
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🔹List of phrasal verb in grade 9 textbook

➡️Unit 1:

* act out: perform something with actions and gestures
* act on: to take action because of something like information received
* act up: behave badly or strangely
* add on: include
* add up: make a mathematical total
* aim at: to target
* allow for: include something in a plan or calculation
* allow of: make possible, permit
* back away: retreat or go backwards
* back down: retract or withdraw your position or proposal in an argument
* back up: make a copy of computer data

➡️Unit 2:

* blow away: to be impressed or amazed by something
* blow off: cancel or neglect something
* blow out: extinguish something (e.g., a candle)
* blow up: explode or destroy something
* boil down to: be summarized or reduced to something essential
* break in: interrupt
* break out: start suddenly (e.g., a war, fire)
* break through: make a significant discovery or achievement
* break down: stop functioning (e.g., a car, machine)
* break off: end a relationship or agreement



➡️Unit 6:

* come across: find something unexpectedly
* come about: happen or occur
* come apart: separate into pieces
* close down: stop operating (e.g., a business)
* come back: return
* come down: fall or descend
* close off: block or restrict access to something
* clear up: become clear or understandable; tidy or clean something

➡️Unit 7:

* drop in: make a short visit
* drop off: deliver something or someone
* drop out: quit or withdraw from something (e.g., school)

➡️Unit 8:

* come through: survive a difficult experience
* come…on: begin to happen or appear
* come in: enter
* come out: be published or released; become known
* comes off: succeeds
* come up with: think of or suggest something
* come over: visit someone’s home
* come down with: become sick with something
* came across: encounter or find something unexpectedly

➡️Unit 9:

* count on: rely on or depend on something
* count up: calculate a total
* crack down (on): take strong action to stop something
* cross off: remove something from a list
* cut back: reduce or decrease something
* cut down: reduce the amount or quantity of something

➡️Unit 10:

* cut out: remove something using scissors or a knife
* cut up: cut something into smaller pieces
* cut off: interrupt or disconnect something
* cut down (on): consume less of something
* deal with: take action to address or resolve something
* do away with: abolish or discard something
* do over: do something again
* do without: manage without something
* doze off: fall asleep
* dress up: wear formal or special clothing
* dress down: wear casual or informal clothing
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UNIT 4. ✨ Cell Reproduction✨

🦸‍♂Cell Cycle

🗼A cell cycle is a sequence of events that takes place in the parent cell
as a means of distributing genetic materials thereby forming daughter cell.
🙋2 main division of cell cycle

🪄 Interphase
🪄 Cell division

🎩 Interphase is divided into 3
❄️ G1 phase( first gap)
During this stage cells are quite active metabolically
🫧they accumulate the building blocks of chromosomal DNA .
❄️ S phase ( synthesis of DNA )

🪄 DNA replication

❄️ G2( Second gap)

🪄Cell replenishes it's energy stores and synthesizes proteins
💡some cell organelles are duplicated during this stage
🧨Cells may continue growing during this phase.
Cell make the final preparations b4 entering into the mitotic phase

👑this Interphase stage is prepare the cell for cell division 👑

The cell Division
🪄it includes necular division karyokinesis followed by cytoplasmic division (cytokinesis) this ultimately results in two identical daughter cells
Each daughter cell grows and starts the cycle the mother cell has undergone.

🤝 Ok guys I think it's clear ya?
So we will continue the next part😌 still that react and support 😘
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