# Voltage Rise and Voltage Drop Testing

**Voltage Rise and Voltage Drop Testing**

In electronics and electrical work there are two kinds of EMF or potential difference. Both are expressed in Volts but they have a somewhat different characteristic. One type of EMF is called voltage rise and the other is called voltage drop. The energy introduced into the circuit is called a voltage rise whereas the energy removed from the circuit by the load is called voltage drop.

A voltage drop is expressed in volts just as in the case with the voltage rise. In fact, if you attempt to measure both a voltage rise and voltage drop a multimeter cannot indicate the difference.

There is, however an important difference between the voltage rise and the voltage drop, if you hold a battery in your hand a potential already exists between the two terminals even though the battery is not connected in the circuit, the voltage rise exists.

One difference between the voltage drop and the voltage rise is that the voltage drop occurs only when the current flows through the load. Thus a battery has a voltage rise whether or not it is connected to a circuit. However a load produces a voltage drop only when current flows through it.

**Voltage Drop Testing**

For example a 10-volt battery with a light bulb connected across it. The battery provides a voltage of 10 volts. As electrons flow through the lamp, a voltage drop is developed across it.

Since the lamp consumes the same amount of energy that the battery provides, the voltage drop across the lamp is equal to the voltage rise across the battery. That is the voltage drop is 10 volts.

Take another example two light bulbs are connected in series across a 10 volt battery. Each bulb drops part of the 10 volts supplied.

If the two lamps are identical, then each one will drop half of the supplied voltage If the two lamps are not identical one bulb will drop more voltage than the other. However, the sum of the voltage drops will always equal the sum of the voltage rises.

Take another example. In this case there are two 4.5 Volt batteries connected in series with the identical lamps. The total voltage rise in the circuit is 9 volts,

Since the lamps are identical each drops one-third of the applied voltage or 3 volts. Note in this case once again the sum of the voltage rises equals the sum of the voltage drops.