# Electric Current Questions and Answers (Q&A) #### J. Lautner

The Biot Savart law is an expression of the magnetic field produced by a steady electric current. Deriving this law entails starting from Maxwell's equations, obtaining and solving Poisson’s equation for all three components of the vector potential.

The Biot Savart law is an equation that describes the magnetic field created by the current carrying wire and allows you to calculate it’s strength at various points. Biot Savart's law deals with the magnetic field induction at a point due to a small current element. It relates to the magnetic field induction at a point due to a low current element. #### J. Lautner

Current flowing in a wire produces a magnetic field around the wire. In a coil, the field from the adjacent turns is the same direction, so it adds up. That is why a coil of wire makes a much stronger magnet than one with fewer turns. The magnetic field line pattern looks very similar to that of a bar magnet.

Flowing current produces its magnetic field. Electricity and magnetism are very closely linked. All closed loop currents create their magnetic fields. If the wire or coil was a magnetic material in its field, the magnetic material may retain a magnetic field when the current wire is stopped. #### J. Lautner

The SI unit for metering an electric current is the ampere, which is the stream of electrical charge across a surface at the ratio of one coulomb for every second. Electric current is gauged using a device called ammeter. Current is the flow of electrons that cause the phenomenon known as electricity and powers our appliances and machines. Current is quantified in amps and resistance is measured in ohms.

The unit of measure for current is amperes. To measure current, you must connect the two leads of the ammeter in the circuit so that the current flows through the ammeter. The best way to measure the current flowing through a simple circuit is to insert your ammeter into the circuit. #### J. Lautner

Joule heating, also known as resistive heating, is caused by electrical currents. It is used in incandescent light bulbs, which are phasing out and being replaced by different types of lighting fixtures. It is also used in motors, inductors, and generators, hot plates, and hair dryers. Any implement that provides heat is joule based. Heat is generated by the movement of electrons and atomic ions as movement and friction cause heat.

Joule heating or ohmic heating is used in the pasteurization process because it produces high temperatures during short periods and this is how milk is pasteurized, which removes the bacteria and makes it safe for drinking. This type of heating is provided through high tension wires and from the energy provider. It is cost effective and very efficient for home heating through the use of heat pumps. #### J. Lautner

Ampere's force law presents that the force of attraction or repulsion between the two wires carrying currents is equivalent to their lengths and the magnitude of current passing through them. If the currents run in a corresponding direction, repulsion takes place. The physical beginning of this force is that each wire produces a magnetic field.

The magnetic field in the space surrounding an electric current is comparable to the change which serves as the source. Ampere's law asserts that for any closed loop path, the sum of the length elements times the magnetic field is equivalent to the permeability times the current. #### J. Lautner

A current can be generated into a conducting loop if it is exposed to a charging magnetic field. You can alter the strength of the magnetic field, move the conductor in and out of the field, and revamp the distance between a magnet and/or conductor. The strength of the stream will vary in proportion to the change of magnetic flux.

The conduction of the flow can be determined by considering Lenz's law, which states that a produced current in the wire will stream in such a way that the magnetic field it generates around the wire will decrease the applied magnetic field. #### J. Lautner

This law was named after Jean Baptist Biot and Felix Savart in 1820. The Biot Savart law is an equation that illustrates the magnetic field made by a current carrying wire, permitting the calculation of its strength at various points. They obtained the mathematical expression for the magnetic flux density.

This is because when a compass is placed near an electric wire, the compass needle tends to change direction. The law is valid in magnetostatic approximation. It is an equation describing the magnetic field generated by a constant electric current. #### J. Lautner

Voltage and current tend to be proportional. It is better to understand that voltage is the force that causes the current, which is the electromotive force. Energy is pushed like pressure pushes water in pipes. The voltage-current will flow. The circuit resists the flow. The more the circuit resists the flow, the less current will flow.

There is an inverse correlation between current and resistance. The current that flows is the result of both the voltage and the resistance of the circuit. The current is proportional to voltage and intensely proportional to current. Typically, in a circuit, the voltage will be reasonably constant and changing the resistances will change the current. #### J. Lautner

The stream or rate of electric charge in a conductor or medium between two points having a deviation in potential is generally expressed in amperes. Current flow is due to the difference of potential between two points. The flow of direction is opposite of electron flow directions.

In electric circuits, this charge is often carried by electrons in a wire. It can also be transmitted by ions in an electrolyte., or by both ions and particles such as in a plasma. It is evident that the resistance to current flow is a constant so that the current flow in the circuit is related to voltage and resistance by Ohm’s law.   