Advertisements
Advertisements
Question
Why should the resistance of:
a voltmeter be very large?
Advertisements
Solution
A voltmeter should have a high resistance so that it can take only a negligible amount of current from the circuit.
APPEARS IN
RELATED QUESTIONS
Define the unit of current.
Three 2 V cells are connected in series and used as a battery in a circuit.
What is the p.d. at the terminals of the battery?
If the amount of electric charge passing through a conductor in 10 minutes is 300 C, the current flowing is:
(a) 30 A
(b) 0.3 A
(c) 0.5 A
(d) 5 A
V1, V2 and V3 are the p.ds. across the 1Ω, 2Ω and 3Ω resistors in the following diagram, and the current is 5 A.
Which one of the columns (a) to (d) shows the correct values of V1, V2 and V3measured in volts?
`V_1` `V_2` `V_3`
(a) 1.0 2.0 3.0
(b) 5.0 10.0 15.0
(c) 5.0 2.5 1.6
(d) 4.0 4.0 2.0
What happens to the other bulbs in a parallel circuit if one bulb blows off?
Two lamps, one rated 40 W at 220 V and the other 60 W at 220 V, are connected in parallel to the electric supply at 220 V.
(a) Draw a circuit diagram to show the connections.
(b) Calculate the current drawn from the electric supply.
(c) Calculate the total energy consumed by the two lamps together when they operate for one hour.
Calculate the equivalent resistance between A and B in the adjacent diagram.
Find the effective resistance in the following circuit diagrams (Fig.):
A 3 pin mains plug is fitted to the lead for a 1 kW electric kettle to be used on a 250 V A.C. supply. Which of the following statements is NOT correct?
(a) A 13 A fuse is the most appropriate value to use.
(b) The brown wire should be connected to the live side of the mains.
The circuit diagram in fig shows two coils of an insulated copper wire wound on a cardboard tube. G is a center zero galvanometer.
(a) Describe what will happen when th e swi tch K is cl osed for severa l
seconds and then opened again .
(b) What will be the effect of repeating the experiment with an iron placed in the tube?
Electrical power P is given by the expression P = (Q × V) ÷ time
(a) What do the symbols Q and V represent?
(b) Express the power P in terms of current and resistance explaining the meanings of symbols used there in.
State the S.I. units of electrical power.
Answer the following question.
An electric lamp of resistance 20 Ω and a conductor of resistance 4 0 are connected to a 6 V battery as shown in the circuit. Calculate: 
(a) the total resistance of the circuit,
(b) the current through the circuit,
(c) the potential difference across the (i) electric lamp and (ii) conductor, and
(d) power of the lamp.
State the condition when it is advantageous to connect cells in parallel.
______ is used to measure the electric current.
Problems for practice:
If 5A current flows through a circuit, then convert the current in terms of microampere?
