# Day 107 (questions)

1) A charge of +6 μC experiences a force of 2 mN in the +x direction at a certain point in space.

(A) What was the electric field there before the charge was placed there?

(B) Describe the force a -2 μC charge would experience if it were used in place of the +6 μC charge.

2) A point charge of -3 x 10-5 C is placed at the origin of coordinates. Find the electric field at the point x = 5 m on the x-axis.

3) Four equal magnitude (4 μC) charges are placed at the four corners of a square that is 20 cm on a side. Find the electric field intensity at the center of the square

(A) if the charges are all positive

(B) if the charges alternate in sign around the perimeter of the square,

(C) if the charges have the following sequence around the square: plus, plus, minus, minus.

4) A 0.200 g ball hangs from a thread in a vertical electric field of 3 kN/C directed upward. What is the charge on the ball if the tension in the thread is (A) zero (B) 4 mN?

5) Determine the acceleration of a proton in an electric field of intensity 500 N/C. How many times is this acceleration greater than that due to gravity?

6) A tiny, 0.60 g ball carries a charge of magnitude 8 μC. It is suspended by a thread in a downward electric field of intensity 300 N/C. What is the tension in the thread if the charge on the ball is (A) positive (B) negative?

7) A tiny ball at the end of a piece of thread is in equilibrium when the thread makes a 20 degree angle with the left side of the vertical. The electric field has a strength of 700 N/C and is directed to the right. The mass of the ball is 6.1 g. What are the magnitude and sign of the charge on the ball?

8) An electron is projected out along the +x axis with an initial speed of 3 x 106m/s. It goes 45 cm and stops due to a uniform electric field in the region. Find the magnitude and direction of the field.

(source)