Question 42:
The table below shows the current in three different electrical appliances when connected to the 240 V mains supply :
(a) Which appliance has the greatest electrical resistance ? How does the data show this ?
(b) The lamp is connected to the mains supply by using a thin, twin-cored cable consisting of live and neutral wires. State two reasons why this cable should not be used for connecting the kettle to the mains supply.
(c) Calculate the power rating of the kettle when it is operated from the 240 V mains supply.
(d) A man takes the kettle abroad where the mains supply is 120 V. What is the current in the kettle when it is operated from the 120 V supply ?
Lakhmir Singh Physics Class 10
Answers
Answer:
Since the above given question is incomplete as the table is not provided, so the table in detail has been provided below:
The table below shows the current in three different electrical appliances when connected to the 240 V mains supply :
Appliance Current
Kettle 8.5 A
Lamp 0.4 A
Toaster 4.8 A
ANSWER:
a) Since current passed is inversely proportional to the resistance of the conductor, so the greatest resistance is possessed by the lamp.
b) i) Due to excessive heating melting down of wire might occur, as large amount of current is drawn by the kettle.
ii) Earthing system is required to maintain safety of a current conducting device which is not here.
c) To calculate power, we apply the formula :
P= VI
P = 240 × 8.5
= 2040 W
d) To calculate the power supply at 120V , we find the value of R [V^2/P], which is = 28.23 ohm [ 240^2/2040]
Now, I= V/R
So, I = 120/28.23
= 4.25 amp
Answer:Since the above given question is incomplete as the table is not provided, so the table in detail has been provided below:
The table below shows the current in three different electrical appliances when connected to the 240 V mains supply :
Appliance Current
Kettle 8.5 A
Lamp 0.4 A
Toaster 4.8 A
ANSWER:
a) Since current passed is inversely proportional to the resistance of the conductor, so the greatest resistance is possessed by the lamp.
b) i) Due to excessive heating melting down of wire might occur, as large amount of current is drawn by the kettle.
ii) Earthing system is required to maintain safety of a current conducting device which is not here.
c) To calculate power, we apply the formula :
P= VI
P = 240 × 8.5
= 2040 W
d) To calculate the power supply at 120V , we find the value of R [V^2/P], which is = 28.23 ohm [ 240^2/2040]
Now, I= V/R
So, I = 120/28.23
= 4.25 amp
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Explanation: