A voltmeter is used to measure the electrical potential difference between two points in a circuit. A digital voltmeter has a numerical display while an analog voltmeter pushes a pointer over a scale in proportion to the circuit’s voltage. Voltmeter calculates the voltage in volts. It operates on the principle that the torque is produced by the current that is induced by the voltage and this torque deflects the instrument’s pointer. The pointer’s deflection is proportional to the potential difference between the two lines. Still voltmeter is not connected in series. Why voltmeter is connected in parallel always?
A voltmeter must be attached in parallel to a device in order to determine the voltage of that device. Since objects in parallel experience the same potential difference.
What is voltmeter used for?
Voltmeter is used to measure potential difference. It is often wired in parallel around the points where the potential difference is to be determined, with one end of the voltmeter connected to point A of a resistance AB and the other end to point B.
Why voltmeter has high resistance?
Resistance defines opposition to current, so high resistance means less current. Voltmeters are designed in such a way that they have high resistance. So clearly, low or negligible amount of current will flow from circuit, which will keep voltage unchanged.
Resistance of voltmeter is always high so that it draws very little current from the circuit. Since voltmeters have a high resistance, so if they are connected in series, it will significantly reduce the current flowing through the circuit.
Why voltmeter is connected in parallel?
You must be familiar with series and parallel combinations already. When electric components are connected in series then same current flows from each instrument but voltage is different. On the other hand, in a parallel combination, voltage is same across each component but current is different from each.
When a voltmeter is connected in parallel with a circuit part, the amount of current flowing through it is minimum. As a result, the voltage in the circuit remains unchanged. If voltmeter connected in series, then it will not be able to measure potential difference as voltage will be varying. Since voltage remains constant in parallel, it can calculate the potential difference between two connected points.
Ammeter connected in series
Since an ammeter tests the electric current in amperes in a branch of a circuit, it always has a low resistance. It must be connected in series with the branch being measured and have a very low resistance to prevent substantial current alternation. Since a voltmeter tests the voltage difference between two points, it has a high resistance, but it does not adjust the amount of current flowing through the element between those two points. As a result, it should have a high level of resistance. If the ammeter is connected in parallel then due to its low resistance, it will act like a short circuit, making the ammeter damaged. The resistance of an ammeter is extremely low. As a result, the current measured in a circuit with an ammeter would be the same as if the ammeter were not present. By connecting an ammeter in series with a circuit, you have effectively short-circuited the circuit you were trying to test.