Cells in series, in parallel and in mixed groups, and the EMF and terminal voltage of a cell. Then the meter bridge for an unknown resistance, and the potentiometer for comparing EMFs and finding an internal resistance.
3 lessons, about 1 h 30 min3 simulations12 problems6 practice questionsPython in every lesson
Created by StemPy LabA cell has an emf and an internal resistance . Cells in series add their emfs when they aid and subtract when they oppose, and their resistances always add. Two unequal cells in parallel act as one cell with and . For identical cells in rows of , the current is greatest when .
A meter bridge is a Wheatstone bridge made with a uniform wire long and a sliding contact. At balance, . The error in from reading the scale is smallest when the balance point is near . Interchanging and and averaging reduces the effect of the end corrections.
A potentiometer is a long uniform wire carrying a steady current, so the potential falls evenly along it: . A cell balanced against a length has , so . A balance with the cell open and with a resistor across it gives . At balance no current is drawn, so the true emf is measured.
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