Page 56 - Physics - XII

Precautions

1. Allow the A.C. current for minimum possible time for safety consideration.
2. Appropriate selection of function switch and range switch for a given measurement of voltage or
current and resistance should be made.
3. Before using the multimeter, its zero ohm should be achieved by connecting its probes together and by

adjusting its knob.
4. While dealing with high voltages, the probes of the multimeter should be held from their insulating cover.
5. While measuring the voltage or current, the range of the multimeter should be selected high, then it is
reduced to low as per the requirement.

6. If the two leads of the multimeter are not identical, then the measurement will be aff ected.

VIVA VOCE

Q1. Can the measurement of D.C. voltage/current be done using A.C. voltage/current function

switch? (NCERT)
Ans. No.

Q2. What is a multimeter?
Ans. It is an electronic device used for measuring A.C./D.C. voltage, D.C. current, and resistance.

Q3. Why is a multimeter also called as AVO meter?
Ans. A multimeter measures current in ampere (A), voltage in volt (V), and resistance in ohm (Ω). So,
it is also called as AVO meter.

ACTIVITY - 3

Aim
To assemble a household circuit comprising three bulbs, three (on/off ) switches, a fuse and a power source.

Apparatus and Materials Required

Three bulbs (40 W, 220 V each), three on-off switches, a fuse of 1.0 A, a plug, fl exible red and black
P.V.C. connecting wires, and main switch

Earth wire

Live wire

S S S
1 2 3 Fuse To A.C.
Socket Mains

B B B
1 2 3
Neutral wire
Fig. 3.1: Household circuit diagram

54