Mastering Physics Set 2 Midterm #1

What is the magnitude of the electric field 1 m away from the positive charge compared to the magnitude of the electric field 2 m away? The magnitude of the electric field 1 m away from the positive charge is- two times equal to one-quarter four times one-half - the magnitude of the electric field 2 m away.

four times

If the field strength is E = 9 V/m a distance of 1 m from the charge, what is the field strength E a distance of 3 m from the charge?

E = 1 V/m

6.58×10^−13 N

Find the magnitude of the electric force, ignoring the sign, that the water molecule exerts on the chlorine ion.

attractive

Is this force attractive or repulsive? attractive repulsive

Make a small dipole by bringing the two charges very close to each other, where they are barely touching. The midpoint of the two charges should still be on one of the grid point intersections (see figure below). Measure the strength of the electric field 0.5 m directly above the midpoint as well as 1 m directly above. Does the strength of the electric field decrease as 1 over distance squared (1/r2)? No, it decreases less quickly with distance. No, it decreases more quickly with distance. Yes, it does.

No, it decreases more quickly with distance.

drag two positive charges, placing them 1 m apart, as shown below. Letâs look at the resulting electric field due to both charges. Recall that the electric field is a vector, so the net electric field is the vector sum of the electric fields due to each of the two charges. Where is the magnitude of the electric field roughly equal to zero (other than very far away from the charges)? The electric field is nonzero everywhere on the screen. The electric field is roughly zero near the midpoint of the two charges. The electric field is zero at any location along a vertical line going through the point directly between the two charges

The electric field is roughly zero near the midpoint of the two charges.

A glass marble is rubbed against a piece of silk. As a result the piece of fabric acquires extra electrons. What happens to the glass marble? Check all that apply. The marble has lost the same number of electrons acquired by the piece of silk. The marble has acquired the same number of electrons acquired by the piece of silk. The marble acquires a positive charge and repels the piece of silk. The marble acquires a positive charge and attracts the piece of silk. The marble acquires a negative charge and attracts the piece of silk. The marble acquires a negative charge and repels the piece of silk.

The marble has lost the same number of electrons acquired by the piece of silk. The marble acquires a positive charge and attracts the piece of silk.

negative

The net electric force on the blue sphere has a magnitude F and is directed in the − y direction. What is the sign of the charge on the yellow sphere? positive negative

qred = q⋅2(d1/d2)^2cos(θ)

The net electric force on the blue sphere has a magnitude F and is directed in the − y direction. Suppose that the magnitude of the charge on the yellow sphere is determined to be 2q. Calculate the charge qred on the red sphere. Express your answer in terms of q, d1, d2, and θ.

positive

The net electric force on the blue sphere has a magnitude F and is directed in the − y direction. What is the sign of the charge on the red sphere? positive negative

negative x

What is the direction of the electric force? negative x positive x

Force on q3 = -6.05×10^−5N

What is the net force exerted by these two charges on a third charge q3 = 54.5 nC placed between q1 and q2 at x3 = -1.210 m ? Your answer may be positive or negative, depending on the direction of the force. Express your answer numerically in newtons to three significant figures.

Make an electric dipole by replacing one of the positive charges with a negative charge, so the final configuration looks like the figure shown below. The electric field at the midpoint is zero. directed to the left. directed to the right.

directed to the right.

The electric field produced by the positive charge is directed radially toward the charge at all locations near the charge. wraps circularly around the positive charge. is directed radially away from the charge at all locations near the charge.

is directed radially away from the charge at all locations near the charge.

Four equal negative point charges are located at the corners of a square, their positions in the xy-plane being (1,1), (−1,1), (−1,−1), (1,−1). The electric field on the x-axis at (1,0) points in the same direction as i^. j^. −i^ −j^

−i^

weakly attractive

(Figure 1) Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D). A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D. Assume throughout this problem that the balls are brought very close together. What is the nature of the force between balls A and C? strongly attractive strongly repulsive weakly attractive neither attractive nor repulsive

strongly attractive

(Figure 1) Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D). A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D. Assume throughout this problem that the balls are brought very close together. What is the nature of the force between balls A and B? strongly attractive strongly repulsive weakly attractive neither attractive nor repulsive

attractive

(Figure 1) Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D). A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D. Assume throughout this problem that the balls are brought very close together. What is the nature of the force between balls A and D? attractive repulsive neither attractive nor repulsive

neither attractive nor repulsive

(Figure 1) Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D). A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D. Assume throughout this problem that the balls are brought very close together. What is the nature of the force between balls D and C? attractive repulsive neither attractive nor repulsive

Consider a point 0.5 m above the midpoint of the two charges. As you can verify by removing one of the positive charges, the electric field due to only one of the positive charges is about 18 V/m. What is the magnitude of the total electric field due to both charges at this location? 36 V/m 25 V/m zero

25 V/m

A K+ ion (mass of 6.5×10^−23 kg) is accelerated through a cell membrane at 1.1 ×10^6 m/s^2. What is the electric field between the membrane walls? 24 N/C 4470 N/C 447 N/C 2.4 N/C

447 N/C

F

Along which lines (A to H) in (Figure 4) should charge 3 be placed so that the free-body diagrams of charge 1, charge 2, and charge 3 are consistent?

C

Along which of the lines (A to H) in (Figure 1) should charge 2 be placed so that the free-body diagrams of charge 1 and charge 2 are consistent? Note that only one of the forces on each charge will be consistent. The other force on each charge will be addressed in Part B with the introduction of charge 3.

D

Along which of the lines (A to H) in (Figure 2) should charge 3 be placed so that the free-body diagrams of charge 1, charge 2, and charge 3 are consistent?

H

Along which of the lines (A to H) in (Figure 3) should charge 2 be placed so that the free-body diagrams of charge 1 and charge 2 are consistent? Note that only one of the forces on each charge will be consistent. The other force on each charge will be addressed in Part D with the introduction of charge 3.

Field lines cannot cross each other. The field lines should be parallel because of the sheet's symmetry

In (Figure 2) , what is wrong with panel B? (Pick only those statements that apply to panel B.) Check all that apply. Field lines cannot cross each other. The field lines should be parallel because of the sheet's symmetry. The field lines should spread apart as they leave the sheet to indicate the weakening of the field with distance. The field lines should always end on negative charges or at infinity.

The field lines should be smooth curves. The field lines should always end on negative charges or at infinity.

In (Figure 3) , what is wrong with panel D? (Pick only those statements that apply to panel D.) Check all that apply. Field lines cannot cross each other. The field lines should turn sharply as you move from one charge to the other. The field lines should be smooth curves. The field lines should always end on negative charges or at infinity.

QA=+7q, QB=−3q

In (Figure 4) , the electric field lines are shown for a system of two point charges, QA and QB. Which of the following could represent the magnitudes and signs of QA and QB? In the following, take q to be a positive quantity. QA=+q, QB=−q QA=+7q, QB=−3q QA=+3q, QB=−7q QA=−3q, QB=+7q QA=−7q, QB=+3q

A=D>F>C>B=E

In the diagram below, there are three collinear point charges: q1, q2, and q3. The distance between q1 and q2 is the same as that between q2 and q3. You will be asked to rank the Coulomb force on q1 due to q2 and q3

has not been in contact with the piece of fabric, which of the following statements best describes the situation when the three marbles are brought together? To keep things simple in this Tutorial, we will ignore the effects of polarization and just focus on the overall charge of each object. Marbles 1 and 2 attract each other, but no interaction occurs with marble 3. Both marbles 1 and 2 attract marble 3. The three marbles will repel each other. Marbles 1 and 2 repel each other, but no interaction occurs with marble 3.

Marbles 1 and 2 repel each other, but no interaction occurs with marble 3.

Make a long line of positive charges, similar to that shown in the figure below. Try to place all of the charges centered along a horizontal grid line. Feel free to look at the electric field, as it is interesting. Measure the strength of the electric field 1 m directly above the middle as well as 2 m directly above. Does the strength of the electric field decrease as 1 over distance squared (1/r2)? No, it decreases more quickly with distance. No, it decreases less quickly with distance. Yes, it does.

No, it decreases less quickly with distance.

Remove the positive charge by dragging it back to the basket, and drag a negative charge (blue) toward the middle of the screen. Determine how the electric field is different from that of the positive charge. Which statement best describes the differences in the electric field due to a negative charge as compared to a positive charge? The electric field changes direction (now points radially inward), but the electric field strength does not change. Nothing changes; the electric field remains directed radially outward, and the electric field strength doesnât change. The electric field changes direction (now points radially inward), and the magnitude of the electric field decreases at all locations

The electric field changes direction (now points radially inward), but the electric field strength does not change.

D

Which of the following panels (labelled A, B, C, and D) in (Figure 2) correctly depicts the field lines from an infinite uniformly negatively charged sheet? Note that the sheet is being viewed edge-on in all pictures. A B C D

B

Which of the following panels (labelled A, B, C, and D) in (Figure 3) shows the correct electric field lines for an electric dipole? A B C D

Now, let's look at how the distance from the charge affects the magnitude of the electric field. Select Show numbers on the green menu, and then click and drag one of the orange E-Field Sensors. You will see the magnitude of the electric field given in units of V/m (volts per meter, which is the same as newtons per coulomb). Place the E-Field Sensor 1 m away from the positive charge (1 m is two bold grid lines away if going in a horizontal or vertical direction), and look at the resulting field strength. Consider the locations to the right, left, above, and below the positive charge, all 1 m away. For these four locations, the magnitude of the electric field is: greatest below the charge. greatest to the left of the charge. the same. greatest to the right of the charge. greatest above the charge.

the same.