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When a charged particle traverses a closed path in an electrostatic field in space, the total work done on the particle is zero. The electric field is conservative. Associated with each point in the field, there is a fixed value of the electrical potential.
In a simple circuit consisting of a chemical cell and a resistor, as shown in Figure 27-1, we have seen that the current flows through the resistor from the positive terminal of the cell to the negative terminal of the cell. The positive terminal is at the higher potential, so that the current flows from the higher to the lower potential outside the cell, but inside the cell the direction of current flow is from the lower to the higher potential. The cell must do work upon the charge in order to raise its potential.