Physics · Current Electricity · NEET
Physically, in a metal wire it is the electrons (negative charge) that actually move. But by an old convention set before electrons were discovered, we define the current direction as the direction a positive charge would move. So current is the flow of charge, and its named direction is the direction of positive charge flow, which is opposite to the electron motion.
Scientists fixed the current direction (from + terminal to - terminal in the outer circuit) long before they knew electrons carry the charge and are negative. When electrons were found to move from - to +, the old convention was kept. So conventional current and electron drift are always opposite. For NEET, always use conventional current unless the question clearly asks about electron motion.
Electric current is a scalar. Even though we talk about its direction, it does not follow vector addition (currents at a junction add by simple algebra using Kirchhoff's junction rule, not by the parallelogram law). Only current density J is a vector. This is a very common NEET trap.
In the external circuit (the wires and bulb), conventional current flows from the positive terminal to the negative terminal. Inside the cell, the current flows from the negative terminal to the positive terminal, driven by the emf. So the current forms one complete closed loop.
It means how much charge passes through a cross-section of the wire in each second. If charge Q flows in time t, the average current is I = Q / t. If 2 coulomb passes a point every 1 second, the current is 2 ampere. More charge per second means larger current.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Electric current is the rate of flow of electric charge through a cross-section of a conductor. In symbols, I = Q / t, where Q is the charge and t is the time.
Conventional current is the current whose direction is taken as the direction of flow of positive charge, that is from the positive terminal to the negative terminal in the external circuit. It is opposite to the actual electron flow.
It is a scalar quantity. It has a direction of flow but does not obey the laws of vector addition. Current density is the related vector quantity.
Free electrons carry the current in a metal. These loosely bound outer electrons drift slowly through the metal when a voltage is applied across the wire.
No. A static charge sitting still produces no current. There must be a net flow of charge across a section for a current to exist.
