1. Two sections of current-carrying wires, $X$ and $Y$, that lie in the plane of the paper, are shown below. The arrow in wire $X$ shows the direction of conventional current. Which response gives possible directions of current in wire $Y$ and electromagnetic force acting on $Y$?

2. A satellite of mass $m$ is in an orbit at a height $h$ from the surface of a planet of mass $M$. The centripetal force acting on the satellite is $F$ and the linear speed is $v$.

What is the new centripetal force and linear orbital speed when it is moved to a new orbit at $2h$ from the surface of the planet?

3. A beam of electrons enters a uniform electric field, as shown.

What effect does this field have on the horizontal and vertical components of the electrons' velocity?

4. Two stars of equal mass $M$ are shown in the diagram, distance $d$ apart. A planet is equidistant from the two stars, with distance d/2 across the midpoint of the line joining the stars as shown.

What is the resultant gravitational field strength at the position of the planet due to the two stars?

5. A satellite $X$ is in a circular orbit of radius $R$ with a period $T$ around Earth.

What will be the orbital radius of satellite Y, travelling in a circular orbit with a period of 8$T$ around Earth?

6. A satellite is in a circular orbit of radius $R$ around a planet of mass $M$. Which of the following graphs represents the relationship between the centripetal acceleration of the satellite and its orbital radius?

A.				B.
C.				D.

7. Planet $X$ has radius $R$ and density $\rho$. The gravitational field strength at the surface of Planet $X$ is $g$.

What is the ratio of the gravitational field strength at the surface of planet Y, which has radius 0.25$R$ and density 3$\rho$, to that at the surface of Planet X?

8. A source of radiation is near a magnetic field that is directed into the page. A sheet of paper is placed in the path of the radiation before it enters the magnetic field.

The gamma radiation is not deflected when entering the magnetic field. Which of the following is correct about the other type of radiation that penetrates the paper sheet and the direction of its deflected path in the magnetic field?

9. A wire is carrying a current $I$ is placed in a region of uniform magnetic field B1. The magnitude of the magnetic field is $B$, and its direction is into the page. The force acting on the wire is $F$, as shown in the diagram.

The wire, carrying the same current $I$, is now placed with the orientation shown into another region of uniform magnetic field B2. The magnitude of the magnetic field is $B$, and its direction is out of the page.

What is the correct direction and magnitude of the force acting on the wire in field B2?

	Direction	Magnitude
A.		$F$
B.		$F$
C.		$F\sin \theta$
D.		$F\sin \theta$

10. Which of the following is correct about the gravitational field strength at a point near a planet?

11. The diagram shows the gravitational field between two masses m1 and m2.

Which of the following is correct?

12. Estimate the speed of an alpha particle that has accelerated from rest in a uniform electric field E=50NC^−1 over a distance of 2.0m.

13. An astronaut in a space station orbiting the earth experiences weightlessness.

The following are three statements about the astronaut and the space station:

• I.  The astronaut experiences no gravitational force.
• II.  The centripetal acceleration of the space station is equivalent to the gravitational field strength at that location
• III.  Both the astronaut and the space station have the same acceleration.

Which of these statements is correct?

14. Two charges separated by a distance $r$ are placed in a medium with permittivity $ϵ$. The charges are then moved to air so that they have the same force between them as that in the medium.

15. A point charge is moved between two parallel plates separated by a distance of $5cm$. The potential difference between the points is $50V$.

What is the average electric field E?

16. Two point charges are separated by a distance $r$ as shown.

17. Satellites $A$ and $B$ orbit the same planet of mass $M$. Satellite $A$ has a mass of $3m$ and it is located at a height of $R$ from the surface of the planet. Satellite $B$ has a mass of $m$ and it is located at a height of 2$R$ from the surface of the planet.

What is the ratio of the centripetal force acting on $A$ to the centripetal force acting on $B$?

18. Two charges, separated by a large distance, are shown below, along with the electric field lines around each charge.

Which of the following statements is correct?

• I.  The charge $q$ is positive.
• II.  The charge $q$ is equal in magnitude to $+Q$.
• III.  The electric field magnitude near the charge $q$ is greater than the magnitude of the field near the charge $+Q$.

19. A hydrogen nucleus is held stationary in a uniform vertical electric field, represented by the arrows. Which of the paths shown would require the largest work to be done on the hydrogen nucleus?

20. Two objects A and B are separated by a distance $r$. The mass of A is much larger than that of B.

Which of the following is correct about magnitude and direction of the gravitational force exerted by A on B compared to that exerted by B on A?

21. Two positive charges of magnitude $2C$ and $8C$ respectively are placed 9cm apart. A third charge is introduced between the two charges as shown below;

At what separation, X, from the 2C charge is the electric field strength equal to zero?

22. In the following diagram, the size of the charges is small compared to the distance R.

What is the direction of the force on the charge in the center?

23. The gravitational field strength on the surface of the moon is gE/6. Two objects of different masses $m$ and $2m$ are released with zero speed on the moon from heights of $h$ and $2h$, respectively, where $h$ is small compared to the radius of the moon.

What are the magnitudes of the accelerations of these objects right after release?

24. Two positive charges q1 and q2 are separated by a distance $d$. A third positive charge $q$ is placed at a distance d/4 from q1 so that the charge $q$ is in equilibrium.

What is the ratio q1/q2?

25. A plastic rod carrying a uniformly distributed positive charge is bent into a quarter-circle. What is the direction of the electric field at point $P$?