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A current in a wire or circuit element can flow in either of two directions. When defining a variable to represent the current, the direction representing positive current must be specified, usually by an arrow on the circuit schematic diagram. [12] [13]: 13 This is called the reference direction of the current .
Illustration of the "reference directions" of the current (), voltage (), and power () variables used in the passive sign convention.If positive current is defined as flowing into the device terminal which is defined to be positive voltage, then positive power (big arrow) given by the equation = represents electric power flowing into the device, and negative power represents power flowing out.
Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for this type of current was galvanic current. [1]
The current in the wire can have two possible directions. Fleming's right-hand rule gives which direction the current flows. The right hand is held with the thumb , index finger and middle finger mutually perpendicular to each other (at right angles), as shown in the diagram.
Fleming's left-hand rule. Fleming's left-hand rule for electric motors is one of a pair of visual mnemonics, the other being Fleming's right-hand rule for generators. [1] [2] [3] They were originated by John Ambrose Fleming, in the late 19th century, as a simple way of working out the direction of motion in an electric motor, or the direction of electric current in an electric generator.
When electricity flows (with direction given by conventional current) in a long straight wire, it creates a cylindrical magnetic field around the wire according to the right-hand rule. The conventional direction of a magnetic line is given by a compass needle. Electromagnet: The magnetic field around a wire is relatively weak. If the wire is ...
If a change in the magnetic field of current i 1 induces another electric current, i 2, the direction of i 2 is opposite that of the change in i 1. If these currents are in two coaxial circular conductors ℓ 1 and ℓ 2 respectively, and both are initially 0, then the currents i 1 and i 2 must counter-rotate. The opposing currents will repel ...
In this case the magnetic field (B, green lines) passes through the righthand wire in the downward direction, so the eddy current (E) circles in a counterclockwise direction. The eddy current flows in the same direction as the main current on the adjacent side of the wire (1) increasing it, but in the opposite direction to the main current on ...