In this article we will discuss about the meaning and laws of resistance to electric current. Meaning of Resistance: Resistance may be defined as that property of a substance which opposes (or restricts) the flow of an electric current (or electrons) through it. The practical as well as mks (or SI) unit of resistance is ohm (Ω), which is defined [...]
In this article we will discuss about the flow of current through series and parallel circuits. Series Circuits: When the resistors are connected end to end, so that they form only one path for the flow of current, then resistors are said to be connected in series and such circuits are known as series circuits. Let resistors R1, R2, and [...]
As the rate of flow of water through a pipe is directly proportional to the effective pressure (i.e., difference of pressure at two ends) and inversely proportional to the frictional resistance, similarly the current flowing through a conductor is directly proportional to the potential difference across the ends of the conductor and inversely proportional to the conductor resistance. This relation [...]
Gustov Robert Kirchhoff derived two basic laws governing the distribution of electric currents in a network, one commonly known as first law or current law (KCL) or point law, whereas the second is called second law or voltage law (KVL) or mesh law. Law # 1. Kirchhoff's First Law or Current Law (KCL) or Point Law: According to this law [...]
The following points highlight the two theorems used for determining the current flowing in a circuit. The theorems are: 1. Maxwell Circulating Current Theorem 2. Node Voltage Theorem. 1. Maxwell Circulating Current Theorem: If a network with several sources has more than two nodes the current in it may be determined by Maxwell circulating current theorem. This is one of [...]
In this article we will discuss about: 1. Meaning of Alternating Current 2. Generation of Alternating Emf 3. Sinusoidal Quantities (Emf, Voltage or Current) 4. Average and Effective (RMS) Values of Alternating Voltage and Current 5. Average and Effective (RMS) Values of Sinusoidal Current and Voltage 6. Form Factor and Peak Factor of Sinusoidal Wave and Other Details. Contents: Meaning [...]
In this article we will discuss about: 1. Introduction to Alternating Quantities 2. Phasor Diagram Using RMS Values 3. Conventions. Introduction to Alternating Quantities: Assumed that alternating voltages and currents follow sine law and generators are designed to give emfs having sine waveform. The above said assumption makes the calculations simple. The method of representing alternating quantities by waveform or [...]
The following points highlight the top seven instruments used for measuring the flow of current. The instruments are: 1. Ammeter 2. Voltmeter 3. Wattmeter 4. Ampere-Hour Meter 5. Watt-Hour Meter or Kilowatt-Hour Meter 6. Insulation Testing Megger or Megger Testing Set or Megger 7. Earth Testing Megger or Megger Earth Tester or Meg Earth Tester. Instrument # 1. Ammeter: The [...]
In this article we will discuss about the disadvantages of ampere-hour meters. Ampere-hour meter actually measures electrical energy in ampere-hour. It is equal to current in ampere flowing through the current coil of the meter multiplied by the time in hour during which the current flows. But as the B.O.T. unit of electrical energy is kilowatt-hour, the scale of the [...]
In this article we will discuss about the connection of voltmeters for the measurement of high voltages. If the supply voltage is high, the resistance of the coil alone may not be sufficient enough to prevent flow of heavy current through the voltmeter. In order that a short-circuit may not occur between the lines at the point of connection, the [...]