Electric-Current

Electric Current – SI Unit, Conventional Direction of Flow & More

What is an Electric current?

Electric current is defined as the rate of flow of negative charges of the conductor. To put it simply, the continuous circulation of electrons in an electrical circuit is called an electrical current. The conducting material consists of a large number of free electrons which move from one atom to the other at random.

SI Unit of Electric Current

Because the charge is measured in coulombs and time in seconds, so the unit of electric current is coulomb/Sec (C/s) or amperes (A). The amperes is the SI unit of the conductor. The “I” is the symbolic representation of the current.

Q= 1C

t= 1s

then

I= 1A

SI-Unit-of-Electric-Cu

Thus, a wire is said to carry a current of one ampere when charge flows through it at the rate of one coulomb per second.

When an electrical potential difference is used throughout the metal wire, the loosely attached free electrons start moving towards the positive terminal of the cell. This constant circulation of electrons constitutes the electrical current. The circulation of currents in the wire is from the negative terminal of the cell to the positive terminal through the external circuit.

Conventional Direction of Flow of Current

According to the electron theory, when the potential difference is applied across the conductor some matter flows through the circuit which makes up the electric current. It was considered that this matter flows from higher potential to lower potential, i.e., positive terminal to the negative terminal of the cell through the external circuit.

Flow-of-Current

This convention of the flow of current is so strongly established that it is still in use. Thus, the standard direction of flow of current is from the positive terminal of the cell to the negative terminal of the cell through the external circuit. The magnitude of the flow of current at any section of the conductor is the rate of flow of electrons i.e., charge flowing per second.

Mathematically, it is represented by

I= Q/t

electric-current-equation-1On the basis of the flow of electric charge the current is mainly categorized into 2 types, i.e., alternating current and direct current. In direct current, the charges flow through unidirectional whereas in alternating current the charges flow in both the direction.

Electron flow

The electron flow is from negative to positive terminal. Electrons are negatively charged and are therefore drawn into the positive terminal as unlike charges attract.

Current is produced by sources such as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type.

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Effect of Electric Current

When an electric current flows through a conductor there are a number of signs which tell that a current is flowing.

Heat is dissipated

Potentially the most obvious is that heat is created. If the current is small then the amount of heat generated is likely to be very small and might not be noticed. Nevertheless, if the current is larger then it is possible that an obvious amount of heat is created.

An electric fire is a prime example showing how a current causes heat to be created. The actual quantity of heat is governed not only by the current, however, also be the voltage and the resistance of the conductor.

Magnetic effect

Another effect that can be noticed is that an electromagnetic field is developed around the conductor. If a current is flowing in the conductor then it is possible to identify this. By putting a compass near to a wire carrying a fairly large amount of direct current, the compass needle can be seen to be deflected.

Note this will not deal with mains because the field is alternating too quickly for the needle to respond and the two wires (live and neutral) close together in the very same cable will cancel out the field.

Magnetic-effect

MCQs

  • What is electric current?
    • A) The rate of flow of positive charges in a conductor
    • B) The rate of flow of negative charges in a conductor
    • C) The rate of flow of protons in a circuit
    • D) The rate of flow of neutrons in a circuit
    • Answer: B) The rate of flow of negative charges in a conductor
  • What is the SI unit of electric current?
    • A) Volts
    • B) Watts
    • C) Amperes
    • D) Coulombs
    • Answer: C) Amperes
  • According to the conventional direction of flow of current, how does current flow in a circuit?
    • A) From negative to positive terminal
    • B) From positive to negative terminal
    • C) From high resistance to low resistance
    • D) From low potential to high potential
    • Answer: B) From positive to negative terminal
  • Which equation represents the mathematical expression for electric current?
    • A) V = IR
    • B) P = VI
    • C) I = Q/t
    • D) R = V/I
    • Answer: C) I = Q/t
  • In which direction does electron flow occur in a circuit?
    • A) From positive to negative terminal
    • B) From high potential to low potential
    • C) From negative to positive terminal
    • D) From low resistance to high resistance
    • Answer: C) From negative to positive terminal
  • What are the two main types of electric current?
    • A) Static and dynamic
    • B) Linear and nonlinear
    • C) Alternating and direct
    • D) Positive and negative
    • Answer: C) Alternating and direct
  • Which effect of electric current results in the creation of heat?
    • A) Magnetic effect
    • B) Chemical effect
    • C) Heating effect
    • D) Electromotive effect
    • Answer: C) Heating effect
  • What happens to a compass near a wire carrying direct current?
    • A) The compass needle remains stationary
    • B) The compass needle deflects
    • C) The compass needle points south
    • D) The compass needle points north
    • Answer: B) The compass needle deflects
  • Which materials are commonly used to produce electric current?
    • A) Plastic and glass
    • B) Metals and alloys
    • C) Ceramics and composites
    • D) Paper and wood
    • Answer: B) Metals and alloys
  • What is the relationship between voltage, current, and resistance described by Ohm’s Law?
    • A) V = IR
    • B) I = VR
    • C) R = IV
    • D) P = VI
    • Answer: A) V = IR
  • What is the unit of electric charge?
    • A) Ampere
    • B) Volt
    • C) Coulomb
    • D) Ohm
    • Answer: C) Coulomb
  • In which direction does heat flow in a conductor when an electric current passes through it?
    • A) From low temperature to high temperature
    • B) From high temperature to low temperature
    • C) It does not flow
    • D) It flows in both directions simultaneously
    • Answer: B) From high temperature to low temperature
  • How is the rate of flow of electric charge represented mathematically?
    • A) R = Q/I
    • B) I = Q/R
    • C) Q = IR
    • D) I = R/Q
    • Answer: B) I = Q/R
  • What determines the quantity of heat generated when an electric current flows through a conductor?
    • A) Only the current
    • B) Only the voltage
    • C) Only the resistance
    • D) Current, voltage, and resistance
    • Answer: D) Current, voltage, and resistance
  • Which effect of electric current is responsible for the operation of electric motors?
    • A) Heating effect
    • B) Magnetic effect
    • C) Chemical effect
    • D) Electromotive effect
    • Answer: B) Magnetic effect
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FAQs on Electric Current and its Properties:

  1. What is electric current?
    • Electric current refers to the flow of negative charges (usually electrons) in a conductor. It is the movement of charge per unit time and is responsible for the flow of energy in electrical circuits.
  2. What is the SI unit of electric current?
    • The SI unit of electric current is the ampere (A), which is equivalent to one coulomb of charge flowing per second.
  3. How is electric current direction conventionally defined?
    • Conventionally, electric current is considered to flow from the positive terminal to the negative terminal of a cell or battery, opposite to the actual flow of electrons. This convention was established early in the study of electricity and is still widely used.
  4. What are the two main types of electric current?
    • Electric current is mainly categorized into two types: direct current (DC), where charges flow unidirectionally, and alternating current (AC), where charges change direction periodically.
  5. What is the direction of electron flow in a circuit?
    • Electrons, being negatively charged, flow from the negative terminal to the positive terminal within a conductor, contrary to the conventional current direction.
  6. What are some sources that produce electric current?
    • Electric current can be produced by various sources such as batteries, thermocouples, solar cells, and dynamo-type electric machines.
  7. What are the effects of electric current?
    • Electric current produces several effects, including the generation of heat and the creation of magnetic fields around conductors through which it flows.
  8. How is heat generated by electric current?
    • Heat is generated in a conductor when electric current flows through it, with the amount of heat depending on the current, voltage, and resistance of the conductor. This effect is known as the heating effect of electric current.
  9. What is the magnetic effect of electric current?
    • When electric current flows through a conductor, it generates a magnetic field around the conductor. This effect is utilized in various applications, including electromagnets and electric motors.
  10. How is electric current mathematically represented?
    • Electric current (I) is mathematically represented by the equation I = Q/t, where Q is the charge passing through a conductor and t is the time taken.
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