What is the voltage drop of a 1.2K ohm?

If you measure the voltage between the DC source and the first resistor (67 ohms), you will notice the voltage potential at the first resistor is 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 you measure the voltage across each resistor, you will measure 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.

You can use Ohm's Law to verify voltage drop. In a DC circuit, voltage equals current multiplied by resistance. Also, Kirchhoff's circuit laws state that in any circuit, the sum of the voltage drops across each component of the circuit is equal to the supply voltage.

In alternating-current circuits, opposition to current flow does occur because of resistance (just as in direct-current circuits). Alternating current circuits also present a second kind of opposition to current flow: reactance. This "total" opposition (resistance "plus" reactance) is called impedance.

The impedance in an alternating-current circuit depends on the spacing and dimensions of the elements and conductors, the frequency of the alternating current, and the magnetic permeability of the elements, the conductors, and their surroundings. The voltage drop in an AC circuit is the product of the current and the impedance (Z) of the circuit. Electrical impedance, like resistance, is expressed in ohms.

Electrical impedance is the vector sum of electrical resistance, capacitive reactance, and inductive reactance. It is expressed by the formula , analogous to Ohm's law for direct-current circuits. Most circuits in a house do not have enough current or length to produce a high voltage drop.

In the case of very long circuits, for example, connecting a home to a separate building on the same property, it may be necessary to increase the size of conductors over the minimum requirement for the circuit current rating. Heavily-loaded circuits may also require a cable size increase to meet voltage drop requirements in wiring regulations. Wiring codes or regulations set an upper limit to the allowable voltage drop in a branch circuit.

In the United States, the 2005 National Electrical Code (NEC) recommends no more than a 5% voltage drop at the outlet. 1 The Canadian electrical code requires no more than 5% drop between service entrance and point of use. 2 UK regulations limit voltage drop to 4% of supply voltage.

Voltage drop of a branch circuit is readily calculated, or less accurately it can be measured by observing the voltage before and after applying a load to the circuit. Excessive voltage drop on a residential branch circuit may be a sign of insufficiently sized wiring or of other faults within the wiring system, such as high resistance connections. Note: voltage drops for installations are specified from the point of common coupling (i.e.

In situations where the circuit conductors span large distances, the voltage drop is calculated. If the voltage drop is too great, the circuit conductor must be increased to maintain the current between the points. The calculations for a single-phase circuit and a three-phase circuit differ slightly.

VD% = Percentage of voltage drop (VD ÷ source voltage x 100). It is this value that is commonly called "voltage drop" and is cited in the NEC 215.2(A)(4) and throughout the NEC. Source voltage = The voltage of the branch circuit at the source of power.

Typically the source voltage is either 120, 208, 240, 277, or 480 V. Important Note: According to NEC 215.2(A)(4) informational note No. 2, the voltage drop for feeders should not exceed 3% and the voltage drop for branch circuits should not exceed 5%, for efficient operation.

Over long distances, larger conductors become expensive, and it is preferable to redesign the circuit to operate at a higher voltage. Doubling the voltage halves the current required to deliver the same amount of power, halving the voltage drop, and an additional doubling in efficiency is realized because that drop is a smaller fraction of the total voltage. This is the motivation for commercial high voltage electrical power distribution, and for the use of the +12V power supply rail for high-power loads in modern personal computers.

^ Rick Gilmour et al. , editor, Canadian Electrical Code Part I, Nineteenth Edition, C22. ^ "Voltage Drop in Installations".

Voltage Drop in Installations - Concepts. Retrieved 8 October 2011. ^ "How to Calculate Voltage Drop".

How to Calculate Voltage Drop.