Explanation​:
The $20nC$ charge produces a leftward electric field in region 1. Therefore, the electric field generated by the $X$ charge should be rightward to cancel the electric field of the 20 nC charge. This is achieved by a negative charge at X. The magnitude of the electric field decreases by distance. All locations in region 1 are closer to point charge $X$ than they are to the $20nC$ charge. Therefore X should be smaller than the charge of $20nC$. The answer is D.

Explanation​:

Using the right-hand rule, one can determine the direction of magnetic fields on loops $Y$ and $Z$ due to the current in the wire.

The magnetic field on loop $Y$ is in the direction out of the page, and the magnetic field on loop $Z$ is in the direction into the page. Both decrease as the current in the wire decreases, so magnetic flux decreases for both loops $Y$ and $Z$.

According to Lenz' law, a current is induced on the loop $Y$ in an anti-clockwise direction, so it opposes the change in the flux. Likewise, according to Lenz' law, a current is induced on the loop Z in a clockwise direction, so it opposes the change in the flux.

Explanation​:
I is correct as the gravitational force is given by F=GMm/r^2​

II is incorrect because gravitational field strength is the gravitational acceleration, which is not equivalent to the force.

III is correct because the gravitational force is the only force acting on the satellite and it provides the centripetal force

Explanation​:
The strong nuclear force is the strongest of the four fundamental forces, then comes electromagnetic, then weak nuclear force and finally gravitation

1/4

Explanation​:
The electric field vector inside a hollow conductor is zero. Due to the lack of field inside the sphere, the electric potential is constant and equal to the surface value . Outward from the surface of the sphere, the electric field varies with the inverse​ square of the distance from the center while electric potential decreases inversely with the distance from the center.

4g

Explanation​:
The negative ion is attracted by the positive charge, therefore its energy at the inner equipotential line is less than the outer one.

Moving from 1 to 2, it moves to a lower energy, therefore work is negative

Moving from 2 to 3, it moves along the same equipotential line, therefore no work done

Moving from 3 to 4, it moves to a higher energy, therefore positive work is done.

According to Fleming’s left hand rule, the electrons in the rod experience a force towards Side B at the top of the rod. The flow of electrons (negative charges) towards the top end of the rod will stop when the electrons at that end are numerous enough to push new electrons back by electrostatic repulsion. That is, an electric field is established in the rod where the top is negative and the bottom is positive. The corresponding field is from the bottom to the top (Side D to Side B)

Explanation​:

Because the electric field lines point toward the charge $q$, this charge must be negative, meaning that statement I is false.

The relatively greater number of field lines around charge $q$ means that this charge magnitude is greater than the charge +Q, indicating that statement II is also untrue.

Electric field line density is proportional to electric field strength. Because the field line density near $q$ is greater than that near $+Q$, statement III is correct.

Therefore the correct answer is option C.

Explanation​:

The hydrogen nucleus is a proton, so it has positive charge.

The electric field lines are pointed upwards, meaning the higher potential is below the nucleus, or meaning that the force on the nucleus is upward.

The question asks for the largest work done, therefore we are looking for the largest displacement parallel and in the opposite direction the field lines. This is shown in D.

Explanation​:

• I. Correct: Since the particle is deflected toward to negative plate it is positively charged.
• II. Correct: In order not to be deflected magnetic force acts on the particle should be upwards. According to the right hand rule the magnetic field should be into the page.
• III. Incorrect: In order not to be deflected magnetic force acts on the particle should be in upwards. According to the right hand rule magnetic field should be into the page.

Explanation​:
Summing the four electric field vectors from the individual point charges, the fields from the charge at the top left and the bottom right will cancel out. The fields from the bottom left and top right will add together to give a net field in the direction of the charge in the top right.

Explanation​:

Induced emf is proportional with rate of change in magnetic flux. As the distance between the bar magnet and loop magnetic flux changes and the rate of change increases as the relative velocity increases (vL>vK=vM​).

Therefore, εL>εK=εM​

Explanation​:
Centripetal acceleration of an orbiting satellite is the gravitational acceleration of the planet, which is given by

g=GM/r^2

Since the gravitational acceleration is inversely proportional to the square of the orbital radius, the correct graphical representation is given in C

Explanation​:

Statement I is incorrect. This is due to Newton’s Law of Gravitation. The astronaut will experience gravitational force from the Earth that acts as the centripetal force.

Since the centripetal force is the gravitational force, then the centripetal acceleration is equal to the gravitational field strength at that point. Therefore both the astronaut and the space station experience the same acceleration. Then statements II and III are correct.

Explanation​:
The alpha particle has positive charge, therefore its deflection will be in the opposite direction of the electron. (answer A or B)

It has a larger mass, therefore the acceleration will be much smaller, explained by the following calculation:

• qE=ma
• a=qE/m​

The alpha particle has twice the charge of the electron, this doubles its acceleration.

It has much more mass than the electron, therefore the denominator in the above ratio increases by a larger factor than the numerator. This means the acceleration of the alpha particle will be much smaller than that of the electron. (its motion will change at a slower rate).

This can also be explained by 2-dimensional motion where there is no force on the horizontal but there is a smaller force on the vertical, meaning it will cover the vertical distance in a longer time, allowing it to travel further along the horizontal, giving the path in B.