Procedure : There are two parts of this activity. Part A deals with the assembling of the continuity testing device (CTD) and Part B deals with checking the effectiveness of earthing. The procedures for these two are given under these two heads.

A. Assembling the Device

Take three pieces of wires about half a meter long each.

Connect one of the terminals of the cell holders to one of the terminals of the bulb holder using a wire.

Connect the second terminal of the bulb holder to second piece of wire. The third piece of wire is attached to the second terminal of the cell holder. Connect a crocodile clip each to the two unconnected ends of the wire.

Insert the cells in the cell holder in proper position, ensuring that the (+) and (-) terminals of the cells are according to the (+) and (-) sign marked on the holder.

Insert the bulb in the bulb holder.

Short the two unconnected terminals and check whether the bulb is glowing or not - if it does not glow, there is a possibility that the bulb is not fitted properly. You can consult your counsellor at this stage. If the bulb glows, your device is ready. Draw a sketch of the device you have assembled in the space provided.

B. Checking the Continuity and Effectiveness of Earthing in an EquipmentIAppliance

Take any appliance, say, a heater or an oven or any instrument used in the lab and locate where the lead is entering the instrument. Open the plate covering it with the help of a screw driver.

You will see three connections there which may be differently placed in different appliances. Locate and identify E, L and N for earth, live and neutral connections, respectively.- If you look closely these are normally written near the connecting screws.

Clamp one of the ends of the continuity testing device on to the earth pin of the plug and other one on the earth connection in the appliance. A bright glowing bulb indicates the continuity.

Repeat the above with live(L) and neutral (N) pins also by connecting the live pin of the plug to the live pin of appliance and the neutral to the neutral.

To check the effectiveness of earthing, fit one end of the CTD to earth pin on the plug and other to the chassis of the appliance. A bright glow indicates good earth while a dim glow means the earthing is poor. The bulb would not glow if there is no earth circuit. Record your observations in the table given in the next subsection.