What is the least possible error encountered when taking measurement with a meter rule?

A charge of one coulomb liberates 0.0033g of copper in an electrolytic process. How long will it take a current of 2A to liberate 1.98g of copper in such a process?

To protect a material from the influence of an external magnetic field, the material should be kept in a

A transformer has 300 turns of wire in the primary coil and 30 turns in the secondary coil. lf the input voltage is 100 volts, the output voltage is