Voltage drop
In electronics, voltage drop is the decrease of electric potential along the path of a current flowing in a circuit. Voltage drops in the internal resistance of the source, across conductors, across contacts, and across connectors are undesirable because some of the energy supplied is dissipated. The voltage drop across the load is proportional to the power available to be converted in that load to some other useful form of energy.
For example, an electric space heater may have a resistance of ten ohms, and the wires that supply it may have a resistance of 0.2 ohms, about 2% of the total circuit resistance. This means that approximately 2% of the supplied voltage is lost in the wire itself. An excessive voltage drop may result in the unsatisfactory performance of a space heater and overheating of the wires and connections.
National and local
Resistive DC voltage drop
Ohm's law can be used to determine the DC voltage drop by multiplying current times resistance: V = I R. Also, Kirchhoff's circuit laws state that in any DC circuit, the sum of the voltage drops across each component of the circuit is equal to the supply voltage.
Consider a direct-current circuit with a nine-volt
If the voltage between the DC source and the first resistor (67 ohms) is measured, the voltage potential at the first resistor will be slightly less than nine volts. The current passes through the conductor (wire) from the DC source to the first resistor; as this occurs, some of the supplied energy is "lost" (unavailable to the load), due to the resistance of the conductor. Voltage drop exists in both the supply and return wires of a circuit. If the voltage drop across each resistor is measured, the measurement will be a significant number. That represents the energy used by the resistor. The larger the resistor, the more energy used by that resistor, and the bigger the voltage drop across that resistor.
Reactive AC voltage drop
AC voltages additionally have a second kind of opposition to current flow: reactance. The sum of resistance and reactance is called impedance.
Electrical impedance is commonly represented by the variable Z and measured in ohms at a specific frequency. Electrical impedance is computed as the
The amount of impedance in an alternating-current circuit depends on the frequency of the alternating current and the magnetic permeability of electrical conductors and electrically isolated elements (including surrounding elements), which varies with their size and spacing.
Analogous to Ohm's law for direct-current circuits, electrical impedance may be expressed by the formula E = I Z. So, the voltage drop in an AC circuit is the product of the current and the impedance of the circuit.
Diode voltage drop
See also
- Brownout (electricity)
- Capacitive dropper
- Electric power distribution
- Electrical resistivity and conductivity
- Ground loop (electricity)
- Kirchhoff's voltage law
- Mesh analysis
- Power cable
- Voltage divider
- Voltage droop
References
- ^ "Voltage drop - maximum, determination, calculation of voltage drop". Archived from the original on 2010-03-06. Retrieved 2010-03-06.
- Electrical Principles for the Electrical Trades (Jim Jennesson) 5th edition