# A confusion with tangent galvanometer

• Rishavutkarsh
In summary: So basically, when you have the coil oriented the way it's supposed to be (with the plane of the coil in the Earth's magnetic north south meridian) then the compass will point true north. But if you rotate the coil by 90 degrees so that the plane of the coil is now perpendicular to the Earth's magnetic field, the compass will then point in a different direction.

#### Rishavutkarsh

When no current is passed through the coil it shows no deflection i.e. B is in the direction shown. But according to theory both fields should be perpendicular (Earth's horizontal field and the one due to coil).
But I am confused because the coil would ideally create a magnetic field that is either parallel or anti-parallel to Earth's Horizontal magnetic field. Is there somewhere I made a blunder or am I missing something?

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Rishavutkarsh said:
But I am confused because the coil would ideally create a magnetic field that is either parallel or anti-parallel to Earth's Horizontal magnetic field.
If that happens, rotate the device by 90 degrees, then they are perpendicular to each other. The orientation of the magnet without current helps to find the right orientation.

What do you mean by "ideally" in this case? I simply don't know why you say that the parallel fields or antiparallel fields configurations are "ideal".

mfb said:
If that happens, rotate the device by 90 degrees, then they are perpendicular to each other. The orientation of the magnet without current helps to find the right orientation.
Yeah that's what I thought too but as far as I know this is the way this device is used (Without rotating it).

Philip Wood said:
What do you mean by "ideally" in this case? I simply don't know why you say that the parallel fields or antiparallel fields configurations are "ideal".
I mean the field lines created by a coil are exactly perpendicular to it's plane 'ideally'.

Rishavutkarsh said:
I mean the field lines created by a coil are exactly perpendicular to it's plane 'ideally'.
That's correct, but it's not what you said before!
You orientate the coil with its plane in the Earth's magnetic North-South meridian plane. So the coil's field (at its centre) is in the East-West direction, that is at right angles to the Earth's field. With no current through the coil a compass (or magnetometer) magnet placed at the centre of the coil will point magnetic North. As soon as you have a current through the coil it will deflect from North.

I got it that's correct; Thank you. I got confused a bit by that compass and magnet.

## 1. What is a tangent galvanometer?

A tangent galvanometer is a scientific instrument used to measure the strength and direction of electric currents. It consists of a circular coil of wire with a magnetic needle at its center.

## 2. How does a tangent galvanometer work?

A tangent galvanometer works by using the interaction between an electric current and a magnetic field. The magnetic needle inside the coil aligns itself with the Earth's magnetic field and is then deflected by the magnetic field created by the electric current. The angle of deflection is used to calculate the strength of the current.

## 3. Can a tangent galvanometer measure both AC and DC currents?

Yes, a tangent galvanometer can measure both AC and DC currents. However, it is more accurate for measuring DC currents as the needle can only respond to changes in the magnetic field, making it difficult to measure rapidly changing AC currents.

## 4. What are some practical applications of a tangent galvanometer?

Tangent galvanometers are commonly used in laboratories for educational purposes and in electrical engineering for calibrating and testing equipment. They can also be used to measure small currents in circuits and to detect the presence of currents in wires.

## 5. How accurate is a tangent galvanometer?

The accuracy of a tangent galvanometer depends on various factors such as the quality of the instrument, external magnetic fields, and the skill of the user. However, with proper calibration and use, it can provide accurate measurements within a few percentage points.