Question

The table below shows the current in three different electrical appliances when connected to the 240 V mains supply Appliance
Current
Kettle
08.5 A
Lamp
0.4 A
Toaster
4.8 A
(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 natural 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 main takes the kettle abroad where the mains supply is 120 V. What is the current is the kettle when it is operated from the 120 V supply?; The table below shows the current in three different electrical appliances when connected to the 240 V mains supply

Answer 1

Explanation:

(a) The light has the highest electrical resistance, since it absorbs the least current.

R = VI and the resistance varies inversely with the current.

(b) Reasons why the mentioned cable should not be used for connecting the kettle to the mains supply.

• The kettle draws considerable pressure. So heating may cause the wire to melt down.
• It needs to have an earthing system for the device to be safe. This is not here.  

(c) The power, P will be:

             P = VI = 240 V × 8.5 A = 2040 W

(d) As the current is directly proportional to the possible difference, having the potential will also reduce the current by half. The new current value is therefore set to be 4.25 A.

$I= \frac{V}{R}$

To find R

$R= \frac{V^{2} }{P}$

=$\frac{240^2}{2040}$   (P =2040)

= 28.23 Ohm

I= V/R = 120/28.23  = 4.25 A

You can get all the answers of Chapter 1 in the link below:    

https://brainly.in/question/14961133

   

Few questions related to this chapter:

State whether an electric heater will consume more electrical energy or les.....

brainly.in/question/14914931

An electric bulb is rated as 10 W, 220 V. How many of these bulbs can be co.....

brainly.in/question/14914929