B.

C.

D.

Correct answer:

2. As shown in the figure, two straight lines ab and cd are connected to an iron ring with equal cross-section everywhere along the radial direction, and the steady current I flows in from the A end and out from the D end, so the integral of the magnetic induction intensity along the closed path L in the figure is equal to ().

A.

B.

C.

D.

Correct answer:

3. There are two annular current-carrying wires A and B with the same radius. They can rotate and move freely and put them in perpendicular positions, as shown in the figure. Which of the following sports meetings takes place?

A, A and B all rotate and translate, and the last two coils have the same current direction and are close together.

B.a does not move, and b rotates and translates under the action of magnetic force.

Both C.A. and B are moving, but the movement trend is uncertain.

Both D.a and B are rotating, but they are not uniform. The magnetic moments of the last two coils are parallel and in the same direction.

Correct answer: A and B both rotate and translate, and the last two coils are in the same direction and close together.

4. A particle with Q charge moves in a uniform magnetic field. Which of the following statements is true?

A as long as the velocity is constant, the Lorentz force on the particle will remain the same.

B. if the charge q becomes -q, the force acting on the particle will be reversed and the value will remain unchanged under the premise of constant speed.

When a particle enters a magnetic field, its kinetic energy and momentum remain unchanged.

D Lorentz force is perpendicular to the velocity direction, so the trajectory of charged particles must be round.

Correct answer: On the premise of constant speed, if the charge Q becomes -q, then the force acting on the particle will be reversed and the value will remain unchanged.

5. The thin wires are evenly and densely wound to grow into an L-shape with a radius of A (L >:>A) The solenoid with a total number of turns of N is filled with a uniform magnetic medium with a relative magnetic permeability of Mr ... If the coil carries a stable current I, the () at any point in the tube

A. the magnitude of magnetic induction intensity is B =? 0 ? rNI

B. What is the magnitude of the magnetic induction intensity? rNI / l

C. the magnetic field strength is H =? 0NI / l

D. the magnetic field strength is h = ni/l.

Correct answer: the magnetic field strength is H = Ni/L.

1. The conductor ball is filled with a uniform dielectric with a relative dielectric constant of ε r. If the field strength near the conductor surface is measured as e, the free charge surface density s on the conductor ball is ().

Year 0E

British Institution of Engineers

C.erE

D.(E 0 r-E 0)

Correct answer: e 0e rE

2. Put a little charge in the center of the spherical shell without electric conductor, and measure the field intensity distribution inside and outside the spherical shell. If this point charge is moved from the center to other positions in the spherical shell, and then the field intensity distribution inside and outside the spherical shell is measured, it will be found that: ()

A. the field intensity distribution inside and outside the spherical shell remains unchanged.

B the field intensity distribution in the spherical shell changes, but it remains unchanged outside the spherical shell.

C the field intensity distribution outside the spherical shell changes, but the field intensity distribution inside the spherical shell remains unchanged.

D the field intensity distribution inside and outside the spherical shell changes.

Correct answer: The field intensity distribution inside the spherical shell changes, but it remains unchanged outside the spherical shell.

3. As shown in the figure, where is it located? Infinite? There is a point charge with a charge of q (q > 0) at a distance d directly above the grounded metal plane, so the electric field intensity at a point near the plane is ().

A.

B.

C.

D.

Correct answer:

4. A parallel plate capacitor, the distance between two plates is d, if a capacitor with the same plate area and thickness of d/2 is inserted, the relative dielectric constant is? R (as shown in the figure), the ratio of capacitance value after dielectric insertion to original capacitance value C/C0 is ().

A.

B.

C.

D.

Correct answer:

5. Is it in a vacuum? Isolated? A uniformly charged sphere and a uniformly charged sphere, if their radius and charge are equal, the relationship between their electrostatic energy is ().

The electrostatic energy of a sphere is equal to that of a sphere.

The electrostatic energy of a sphere is greater than that of a sphere.

The electrostatic energy of a sphere is less than that of a sphere.

D the electrostatic energy inside the ball is greater than that inside the ball, and the electrostatic energy outside the ball is less than that outside the ball.

Correct answer: the electrostatic energy of a sphere is greater than that of a sphere.