5.2-1. At what distance in vacuum from each other will two protons repel each other with a force of 1.00 pN? [15 nm]

5.2-2. If at that distance they repel each other with the force 0.25 pN, what is a) the permittivity [3.54 x 10^-11 C²N^-1m^-1] b) the relative permittivity of the medium they are in? [4]

5.2-3. Two electrons are 1 mm from each other. What is the resultant electric field in a point on a line through them, 0.20 mm from one of them? [34 nVm^-1]

5.3-3. Two parallel metal plates are connected to the terminals of a 4.5 V battery. The homogenous electric field between them is 23 NC^-1. What is the distance between them? [20 cm]

5.4-1. When a DC power source is connected to a 5.00 ohm resistor, the dissipated power is 200 mW. What is a) the current through the resistor [200 mA]b) the potential difference over it ? [1.00 V]

5.4-2. What resistor must be connected in parallel with the one in e4-1 to give a combined resistance of 3.00 W? [7.5 W]

5.4-3. What is then the a) potential differences over the two resistors [What do you think?] b) the currents through them? [0.20 A and 0.13 A]

5.5-1. A battery with the emf 12.00 V gives a terminal voltage of 11.50 V when the current 8.00 A is drawn from it. Find a) its internal resistance [0.06 W] b) the resistance of the external circuit [1.44 W]

5.6-1. How far from a straight wire carrying the current 2.00 A is the magnetic field intensity 2.00 % of that inside a solenoid carrying 1.00 A in 300 loops, and being 7.40 cm long? [3.93 mm]

5.7-1. What force is acting on a 3.00 cm long wire carrying 2.00 nA at an angle of 45 degrees to a 1.20 mT magnetic field? [510 pN]

5.7-2. If the current in e7-1 is carried by electrons moving at 5 % of the speed of light, how many are needed? [25]

5.7-3. A piece of wire has the linear density (mass per length) µ and is falling downwards away from another stationary but identical wire, both carrying the current I. Find an expression for the resultant acceleration of the falling wire as a function of the distance it has fallen away from the upper wire. State at least 3 different assumptions you make. [Depends on assumptions]