O.H.M.S.

Three layers should give you the required number of turns in the secondary winding and a resistance of approximately 3-1/2 ohms.

The resistance of dry cells varies from less than 0.1 of an ohm when new to several ohms when old.

If each lamp when hot has a resistance of 220 ohms, and the E.M.F. is 100 volts, what current will flow?

What will be the current flowing through a voltmeter having 500 ohms resistance in circuit with them?

Find the reactance of a choke coil having a resistance of 10 ohms, when its impedance is 50 ohms.