A science learner wired three identical resistors, two switches, an ammeter, a volte
switches, an ammeter, a voltmeter and a 12
cell into the circuit shown below:
She took readings on the meters with switch S, closed and switch S, open. She then closed s also
and read the meters again. She found that the readings had changed in the following way
Voltmeter
Ammeter
Decreased
(2)
increased
increased
decreased
stayed the same
Increased
Increased
Decreased
Answers
two switches, an ammeter, a volte
switches, an ammeter, a voltmeter and a 12
cell into the circuit shown below:
She took readings on the meters with switch S, closed and switch S, open. She then closed s also
and read the meters again. She found that the readings had changed in the following way
Voltmeter
Ammeter
Decreased
Explanation:
Answer--DECRESED
Ans. • It has a special property that it glows on heating.
• It has ,i high melting point.
• It does not tenet with the gases present in air and does not get oxidized.
• It has a low resistance.
(b) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made up of alloys rather than a pure menu?
Ans. • They offer higher resistance than pure metals, thus heating better.
• They have a high melting point.
• They do not oxidize.
(c) Why is the series arrangement not used for domestic circuits?
Ans. • If any appliance is at fault, then the current is not able to flow through.
• Different appliances have different current requirements, but in series the current is the same. This can cause a power surge, thus damaging the appliances.
• Very long wires m domestic series circuits offer unusually high resistance, which is unwanted.
(d) How does the resistance of a wire vary with its area of cross section?
Ans. The relation between the resistance of a wire and its area of cross-section can be defined as:
• R is inversely proportional to the area of cross-section