Four point charges are arranged in a flat plane and generate an electric field in the space around them. Under which set of conditions, if any, will two or more electric field lines cross each other? A. The four charges are arranged in a straight line.
B. The four charges are identical in magnitude.
C. The four charges form the vertices of a four-sided geometric figure.
D. No conditions; the field lines never cross.

Agalvanometer has an internal resistance of 100 ω and deflects full-scale at 2.00 ma. what size resistor should be added to the galvanometer to convert it to a milliammeter capable of reading up to 4.00 ma, and how should this resistor be connected to the galvanometer?

One day, after pulling down your window shade, you notice that sunlight is passing through a pinhole in the shade and making a small patch of light on the far wall. you see that the patch of light seems to be a circular diffraction pattern. it appears that the central maximum is about 1 cm across and you estimate that the distance from the window shade to the wall is about 3 m. what is (a) the average wavelength of sunlight? (b) the diameter of the pinhole?

Gordon is going for a run through the park, but it is cold outside. the low outside temperature could affect his personal safety.