The correct answer is C. both D.C. and A.C.
A moving iron instrument is a type of electrical instrument that uses the magnetic field of an electric current to move a pointer. It can be used to measure both direct current (DC) and alternating current (AC).
In a moving iron instrument, the current to be measured passes through a coil of wire. This creates a magnetic field that interacts with the magnetic field of a permanent magnet. The interaction of these two magnetic fields causes a pointer to move. The amount of movement of the pointer is proportional to the amount of current flowing through the coil.
Moving iron instruments are relatively simple and inexpensive to manufacture. They are also relatively rugged and can withstand a certain amount of abuse. However, they are not as accurate as other types of instruments, such as moving coil instruments.
Moving iron instruments are typically used to measure small currents, such as those used in household appliances. They are also used in some industrial applications, such as motor control.
Here is a brief explanation of each option:
- Option A: D.C. only. This is incorrect because moving iron instruments can be used to measure both DC and AC.
- Option B: A.C. only. This is incorrect because moving iron instruments can be used to measure both DC and AC.
- Option C: both D.C. and A.C.. This is the correct answer because moving iron instruments can be used to measure both DC and AC.
- Option D: neither D.C. and A.C.. This is incorrect because moving iron instruments can be used to measure both DC and AC.