EduNinjaA long current-carrying wire is at rest in the reference frame S of the laboratory. A positively charged particle P outside the wire moves with velocity v relative to S . The electrons making up the current in the wire move with the same velocity v relative to S .
current-carrying wire
State and explain whether the force experienced by P is magnetic, electric or both
in reference frame S .
The long straight conductor is formed into a coil consisting of two separate turns, X and Y . The coil hangs with its axis vertical.
Assume that the turns of the coil each behave as a long straight conductor.
Explain why, when there is a current in the coil, the separation of X and Y decreases.
The current in the coil is 15 A and the circumference of one turn is 0.48 m . In order to restore X and Y to their original separation, a mass of is suspended from turn Y . Estimate the magnetic field strength at X due to Y .
A3. This question is about radioactivity.
Caesium-137 ( ) is a radioactive waste product with a half-life of 30 years that is formed during the fission of uranium. Caesium-137 decays by the emission of a beta-minus particle to form a nuclide of barium (Ba).
A long straight current-carrying wire is at rest in a laboratory. A negatively-charged particle P outside the wire moves parallel to the current with constant velocity v relative to the laboratory.
In the reference frame of the laboratory the particle P experiences a repulsive force away from the wire.
State the nature of the force on the particle P in the reference frame of the laboratory.
A particle of mass m and positive charge q moves on a circular path with speed v in a vacuum. A uniform magnetic field B is directed into the plane of the page.
Show that the radius R of the circular path is given by .
Suggest why the speed of the particle stays constant, even though a force acts on the particle.
The particle in (b), now moving in a region of magnetic field in air, follows the path shown.
Explain the shape of this path.
Two oppositely charged parallel plates are a distance 8.0 cm apart. The potential difference between the plates is 120 V . An alpha particle is placed on the positively charged plate and released from rest. Gravity is ignored.
Show that the acceleration of the alpha particle is about .
A magnetic field directed into the plane of the page is now established between the plates. An alpha particle enters the region between the plates with a horizontal speed of . The particle is not deflected.
Calculate the magnitude of the magnetic field.
Two parallel current-carrying wires have equal currents in the same direction. There is an attractive force between the wires.
Identify the nature of the attractive force recorded by an observer stationary with respect to the wires.
A wire carries an electric current. An external electron e moves with the drift velocity v of the electrons in the wire. Observer O is at rest relative to the wire.
State and explain the nature of the electromagnetic force acting on electron e in the frame of reference of
observer O .
The ampere is defined in terms of
power dissipated in a wire of known length, cross-sectional area and resistivity.
potential difference across a resistance of known value.
number of electrons flowing past a point in a circuit in a given time.
force per unit length between parallel current-carrying conductors.
A proton is moving in a region of magnetic field of strength B. The speed of the proton relative to the magnetic field is v.
In the reference frame in which the magnetic field is at rest, the proton experiences an initial magnetic force e v B upwards.
Outline why there can be no magnetic force on the proton in the proton's rest frame.
This question is in two parts. Part 1 is about electric fields and radioactive decay. Part 2 is about change of phase.
Part 1 Electric fields and radioactive decay
Protons travelling with a speed of enter the region between two charged parallel plates X and Y . Plate X is positively charged and plate Y is connected to earth.
A uniform magnetic field also exists in the region between the plates. The direction of the field is such that the protons pass between the plates without deflection.
State the direction of the magnetic field.
The magnitude of the magnetic field strength is . Determine the magnitude of the electric field strength between the plates, stating an appropriate unit for your answer.