A torch has a battery, a switch and a bulb. Close the switch, and the bulb lights. In this course we find what flows in the wire, what pushes it, and how the current, the push and the resistance are connected by Ohm's law.
3 lessons, about 1 h 15 min3 simulations12 problems6 practice questionsPython in every lesson
Created by StemPy LabElectric current is the flow of electric charge. It is measured in ampere, and . The conventional current goes from the positive to the negative terminal of a cell, and the electrons move the other way. A circuit is a closed path. An ammeter in series measures the current.
Charge flows when there is a potential difference between two points, as water flows when there is a difference of level. The potential difference between two points is the work done to move a unit charge: . It is measured in volt, and 1 V = 1 J/C. A voltmeter is connected in parallel.
Ohm's law says that the current through a conductor is proportional to the potential difference across it, at a constant temperature. So is a constant, which is the resistance of the conductor: . The unit of resistance is the ohm. The graph of V against I for a conductor that obeys Ohm's law is a straight line through the origin.
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