An electric catfish can generate a significant potential difference using stacks of special cells called electrocytes. Each electrocytes develops a potential difference of 110 mV. How many cells must be connected in series to give the 350 V a large catfish can produce?

When a nerve cell depolarizes, charge is transferred across the cell membrane, changing the potential difference. For a typical nerve cell, 9.0 pC of charge flows in a time of 0.50 ms. What is the average current?

Wires 1 and 2 are made of the same metal. Wire 2 has twice the length and twice the diameter of wire 1. What are the ratios (a) $\rho _ { 2 } / \rho _ { 1 }$ of the resistivities and (b) $R _ { 2 } / R _ { 1 }$ of the resistance of the two wires?

A 70 W electric blanket runs at 18 V. a. What is the resistance of the wire in the blanket? b. How much current does the wire carry?

Three wires meet at a junction. Wire 1 has a current of 0.40 A into the junction. The current of wire 2 is 0.65 A out of the junction. (a) How many electrons per second move past a point in wire 3? (b) In which direction do the electrons move -- into or out of the junction?

A wire carries a $15 \mu \mathrm { A }$ current. How many electrons pass a given point on the wire in 1.0 s?