Physics Test
For the graph shown in the figure what physical quantity does the slope of the graph represent for a DC circuit? (Potential on the x axis and Power on the y axis
Current
Suppose you wanted to hold up an electron against the force of gravity by the attraction of a fixed proton some distance above it. How far above the electron would the proton have to be? (k = ¼ (pi)e_0 = 9.0 x 10^9 N*m^2/C^2, e= 1.6 x 10^-19 C, mass of proton = 1.67 x 10^-27 kg, mass of electron = 9.11 x 10^-31 kg)
5.1 m
Two electrons are 20.0 mm apart at closest approach. What is the magnitude of the maximum electric force that they exert on each other? (e = 1.60 x 10^-19 C, k =¼(pi)e_0= 9.0 x 10^9 N x m^2/C^2)
5.8 x 10^-27 N.
How many electrons are necessary to produce 1.0 C of negative charge? (e = 1.60 x 10^-19 C)
6.3 x 10^18
Three equal charges +Q are at three dod the corners of a square of side d. A fourth charge +Q of equal magnitude the center of the square as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the center of the square?
B
Three equal negative point charges -1 are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the vacant corner of the square?
B
A battery charges a parallel-plate capacitor fully and then is removed. The plates are then slowly pulled apart. What happens to the potential difference between the plates as they are being separated?
It increases
The length of certain wire is doubled and at the same time its radius is reduced by a factor of 2. What is the new resistance of this wire?
It is 8 times as large
As an electron moves in the direction the electric field lines:
It is moving from high potential to low potential and gaining electric potential energy.
The length of a certain wire is kept the same when its radius is doubled. What is the new resistance of this wire?
It is reduced by a factor 4
The figure shows electric field lines arising from two small charged particles P and Q. Consider the following two statements: (i) the charge on P is smaller than the charge on Q, or (ii) the electrostatic force on P is smaller than the force on Q.
Only (i) is true.
If the current flowing through a circuit of constant resistance is doubled, the power dissipated by that circuit will...
Quadruples in magnitude
For the graph shown in the figure what physical quantity does the slope of the graph represent for ohmic material? (Potential on the y-axis and Current is the x-axis).
Resistance
If two objects are electrically attracted to each other:
The objects could be electrically neutral.
An electron is initially moving to the right when it enters a uniform electric field directed upwards, as shown in in the figure. Which trajectory (X,Y,Z, or W) will the electron follow in the field?
Z
When a current flows through a metal wire, the moving charges are
only electrons
Two stationary point charges q1 and q2 are shown in the figure along with a sketch of some field lines representing the electric field produced by them. What can you deduce from the sketch?
q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2.
In outer space, a positive charge q is released near a positive fixed charge Q, as shown in the figure. As q moves away from Q, what is true about the emotion of q? (There may be more than one correct choice.)
It will move with increasing speed. It will move with decreasing acceleration.
Consider two copper wires of equal length. One wire has twice the cross-sectional area of the other. How do the resistances of these two wires compare?
The thicker wire has one-half the resistance of the thinner wire.
X and Y are two initially uncharged metal spheres on insulating stands, and they are in contact with each other. A positively charged rod R is brought close to X as shown in part (a) of the figure. Sphere Y is now moved away from X, as shown in part (b). What are the final charge states of X and Y?
Y is positive X is negative
