| Date | November 2016 | Marks available | 4 | Reference code | 16N.3.SL.TZ0.4 |
| Level | Standard level | Paper | Paper 3 | Time zone | 0 - no time zone |
| Command term | Explain and State | Question number | 4 | Adapted from | N/A |
Question
An electron X is moving parallel to a current-carrying wire. The positive ions and the wire are fixed in the reference frame of the laboratory. The drift speed of the free electrons in the wire is the same as the speed of the external electron X.
Define frame of reference.
In the reference frame of the laboratory the force on X is magnetic.
(i) State the nature of the force acting on X in this reference frame where X is at rest.
(ii) Explain how this force arises.
Markscheme
a coordinate system
OR
a system of clocks and measures providing time and position relative to an observer
OWTTE
i
electric
OR
electrostatic
ii
«as the positive ions are moving with respect to the charge,» there is a length contraction
therefore the charge density on ions is larger than on electrons
so net positive charge on wire attracts X
For candidates who clearly interpret the question to mean that X is now at rest in the Earth frame accept this alternative MS for bii
the magnetic force on a charge exists only if the charge is moving
an electric force on X , if stationary, only exists if it is in an electric field
no electric field exists in the Earth frame due to the wire
and look back at b i, and award mark for there is no electric or magnetic force on X
Examiners report
Syllabus sections
- 17N.3.SL.TZ0.4: Outline the conclusion from Maxwell’s work on electromagnetism that led to one of...
- 19M.3.SL.TZ1.3b: State the speed of the flash of light according to an observer on the ground using Maxwell’s...
- 19M.3.SL.TZ1.3a: State the speed of the flash of light according to an observer on the ground using Galilean...
-
18M.3.SL.TZ1.4a.i:
Calculate, according to Galilean relativity, the time taken for a muon to travel to the ground.
-
18M.3.SL.TZ2.3a.i:
Calculate, for the reference frame of rocket A, the speed of rocket B according to the Galilean transformation.
-
17M.3.SL.TZ2.3b:
A current is established in a long straight wire that is at rest in a laboratory.
A proton is at rest relative to the laboratory and the wire.
Observer X is at rest in the laboratory. Observer Y moves to the right with constant speed relative to the laboratory. Compare and contrast how observer X and observer Y account for any non-gravitational forces on the proton.
-
17M.3.SL.TZ2.3a:
State one prediction of Maxwell’s theory of electromagnetism that is consistent with special relativity.
-
18N.3.SL.TZ0.4b.i:
Determine the time it takes the probe to reach the front of the rocket according to an observer at rest in the rocket.
-
18N.3.SL.TZ0.3b.ii:
hence show that the space coordinate of E in frame S is .
- 18N.3.SL.TZ0.3a: State what is meant by a reference frame.
-
18M.3.SL.TZ1.3b.ii:
Deduce whether the overall field around the wire is electric, magnetic or a combination of both according to observer Y.
-
17M.3.SL.TZ1.3a:
State what is meant by a reference frame.
-
17M.3.SL.TZ1.3b.ii:
State and explain whether the force experienced by P is magnetic, electric or both, in the rest frame of P.
- 16N.3.SL.TZ0.4a: Define frame of reference.
- 19N.3.SL.TZ0.3b(i): State the nature of the force on the particle P in the reference frame of the laboratory.
-
19N.3.SL.TZ0.3b(ii):
Deduce, using your answer to part (a), the nature of the force that acts on the particle P in the rest frame of P.
-
19N.3.SL.TZ0.3b(iii):
Explain how the force in part (b)(ii) arises.
-
17M.3.SL.TZ1.3b.i:
State and explain whether the force experienced by P is magnetic, electric or both, in reference frame S.
-
19M.3.SL.TZ1.4a.i:
Estimate in the Earth frame the fraction of the original muons that will reach the Earth’s surface before decaying according to Newtonian mechanics.
-
18M.3.SL.TZ1.3a:
State whether the field around the wire according to observer X is electric, magnetic or a combination of both.
-
18N.3.SL.TZ0.3b.i:
explain why the time coordinate of E in frame S is .
- 20N.3.SL.TZ0.3b: State a postulate that is the same for both special relativity and Galilean relativity.
- 20N.3.SL.TZ0.3c(i): Identify the nature of the attractive force recorded by an observer stationary with respect...
- 20N.3.SL.TZ0.4a: The Lorentz transformations assume that the speed of light is constant. Outline what the...
- 20N.3.SL.TZ0.3a: Maxwell’s equations led to the constancy of the speed of light. Identify what Maxwell’s...
- 20N.3.SL.TZ0.3c(ii): A second observer moves at the drift velocity of the electron current in the wires. Discuss...
- 19M.3.SL.TZ2.5b: Explain why there is no magnetic force on each proton in its own rest frame.
- 19M.3.SL.TZ2.5c: Explain why there must be a resultant repulsive force on the protons in all reference frames.
- 19M.3.SL.TZ2.4ai: Define an inertial reference frame.
- 19M.3.SL.TZ2.4aii: As the spaceship passes the Earth it emits a flash of light that travels in the same...
-
19M.3.SL.TZ2.4b:
Use your answer to (a)(ii) to describe the paradigm shift that Einstein’s theory of special relativity produced.
- 19M.3.SL.TZ2.5a: Outline why there is an attractive magnetic force on each proton in the laboratory frame.
-
18M.3.SL.TZ1.4a.ii:
Deduce why only a small fraction of the total number of muons created is expected to be detected at ground level according to Galilean relativity.
