Goyal Brothers Textbook Solutions: Electric Energy Power Household Circuits

 Page 1


https://www.ncertbooksolutions.com
Electric Energy, Power & Household Circuits 
 
Exercise – 1 
Question 1. 
(a) What do you understand by the term electric work ? 
Answer: 
Electric work : “Electric work is said to be done when an electric charge flows through a 
conductor, at some potential difference.” 
 
(b) State and define SI unit of electric work. 
Answer: 
S.I. unit of electric work ? Joule (J) 
1J = 1 volt × 1 coulomb 
1 Joule : “Is the amount of work done when a charge of one coulomb flows through a 
conductor at a pot. diff. of 1 volt.” 
(c) Name two bigger units of electric work. How are they related to SI unit ? 
Answer: 
Two bigger units of electric work : 
1. Kilo – Joule (kJ) = 10
3
 J 
2. Mega-joule (Mj) = 10
6
 J 
Question 2. 
Derive an expression for electric work connecting : 
(a) Current, resistance and time 
(b) Current, potential difference and time. 
(c) Potential difference, resistance and time. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
Page 2


https://www.ncertbooksolutions.com
Electric Energy, Power & Household Circuits 
 
Exercise – 1 
Question 1. 
(a) What do you understand by the term electric work ? 
Answer: 
Electric work : “Electric work is said to be done when an electric charge flows through a 
conductor, at some potential difference.” 
 
(b) State and define SI unit of electric work. 
Answer: 
S.I. unit of electric work ? Joule (J) 
1J = 1 volt × 1 coulomb 
1 Joule : “Is the amount of work done when a charge of one coulomb flows through a 
conductor at a pot. diff. of 1 volt.” 
(c) Name two bigger units of electric work. How are they related to SI unit ? 
Answer: 
Two bigger units of electric work : 
1. Kilo – Joule (kJ) = 10
3
 J 
2. Mega-joule (Mj) = 10
6
 J 
Question 2. 
Derive an expression for electric work connecting : 
(a) Current, resistance and time 
(b) Current, potential difference and time. 
(c) Potential difference, resistance and time. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
https://www.ncertbooksolutions.com
Answer: 
 
 
Question 3. 
State three factors which determine the quantity of heat produced in a conductor. 
Answer: 
Three factors which determine heat produced in a conductor : 
Heat produced = Energy Work done 
W=H=I
2
Rt 
? Three factors are I — current 
R — Resistance of conductor 
t — time for which current flows. 
Question 4. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
Page 3


https://www.ncertbooksolutions.com
Electric Energy, Power & Household Circuits 
 
Exercise – 1 
Question 1. 
(a) What do you understand by the term electric work ? 
Answer: 
Electric work : “Electric work is said to be done when an electric charge flows through a 
conductor, at some potential difference.” 
 
(b) State and define SI unit of electric work. 
Answer: 
S.I. unit of electric work ? Joule (J) 
1J = 1 volt × 1 coulomb 
1 Joule : “Is the amount of work done when a charge of one coulomb flows through a 
conductor at a pot. diff. of 1 volt.” 
(c) Name two bigger units of electric work. How are they related to SI unit ? 
Answer: 
Two bigger units of electric work : 
1. Kilo – Joule (kJ) = 10
3
 J 
2. Mega-joule (Mj) = 10
6
 J 
Question 2. 
Derive an expression for electric work connecting : 
(a) Current, resistance and time 
(b) Current, potential difference and time. 
(c) Potential difference, resistance and time. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
https://www.ncertbooksolutions.com
Answer: 
 
 
Question 3. 
State three factors which determine the quantity of heat produced in a conductor. 
Answer: 
Three factors which determine heat produced in a conductor : 
Heat produced = Energy Work done 
W=H=I
2
Rt 
? Three factors are I — current 
R — Resistance of conductor 
t — time for which current flows. 
Question 4. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
https://www.ncertbooksolutions.com
(a) What do you understand by the term electric power ? 
(b) State SI unit of electric power and define it 
(c) Name two bigger units of electric power and their relation with SI unit. 
Answer: 
 
 
Question 5. 
Derive an expression for electric power connecting : 
(a) Current and resistance. 
(b) Current and potential difference. 
(c) Potential difference and resistance. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
Page 4


https://www.ncertbooksolutions.com
Electric Energy, Power & Household Circuits 
 
Exercise – 1 
Question 1. 
(a) What do you understand by the term electric work ? 
Answer: 
Electric work : “Electric work is said to be done when an electric charge flows through a 
conductor, at some potential difference.” 
 
(b) State and define SI unit of electric work. 
Answer: 
S.I. unit of electric work ? Joule (J) 
1J = 1 volt × 1 coulomb 
1 Joule : “Is the amount of work done when a charge of one coulomb flows through a 
conductor at a pot. diff. of 1 volt.” 
(c) Name two bigger units of electric work. How are they related to SI unit ? 
Answer: 
Two bigger units of electric work : 
1. Kilo – Joule (kJ) = 10
3
 J 
2. Mega-joule (Mj) = 10
6
 J 
Question 2. 
Derive an expression for electric work connecting : 
(a) Current, resistance and time 
(b) Current, potential difference and time. 
(c) Potential difference, resistance and time. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
https://www.ncertbooksolutions.com
Answer: 
 
 
Question 3. 
State three factors which determine the quantity of heat produced in a conductor. 
Answer: 
Three factors which determine heat produced in a conductor : 
Heat produced = Energy Work done 
W=H=I
2
Rt 
? Three factors are I — current 
R — Resistance of conductor 
t — time for which current flows. 
Question 4. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
https://www.ncertbooksolutions.com
(a) What do you understand by the term electric power ? 
(b) State SI unit of electric power and define it 
(c) Name two bigger units of electric power and their relation with SI unit. 
Answer: 
 
 
Question 5. 
Derive an expression for electric power connecting : 
(a) Current and resistance. 
(b) Current and potential difference. 
(c) Potential difference and resistance. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
https://www.ncertbooksolutions.com
Answer: 
 
 
 
Question 6. 
(a) What do you understand by term electric energy ? 
(b) Name and define the smallest commercial unit of electric energy. 
(c) Name and define the standard commercial unit of electric energy. 
Answer: 
(a) Electric energy : E = P × t = VIt 
“Electric energy is the product of power and time.” i.e. electric energy consumed by an 
electrical appliance is produced of ‘power rating’ and ‘time’ for which it is used. 
(b) Unit of electric energy ? Joule (J) 
S.I. unit of electric work ? Joule (J) 
1J = 1 volt × 1 coulomb 
1 Joule : “Is the amount of work done when a charge of one coulomb flows through a 
conductor at a pot. diff. of 1 volt.” 
(c) Standard Commercial unit of Electric Energy : Kilo-watt-Hour 1 kwH : “Is the amount 
of electrical energy consumed when an electrical appliance having a power rating of 1 
kilowatt is used for 1 hour.” 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
Page 5


https://www.ncertbooksolutions.com
Electric Energy, Power & Household Circuits 
 
Exercise – 1 
Question 1. 
(a) What do you understand by the term electric work ? 
Answer: 
Electric work : “Electric work is said to be done when an electric charge flows through a 
conductor, at some potential difference.” 
 
(b) State and define SI unit of electric work. 
Answer: 
S.I. unit of electric work ? Joule (J) 
1J = 1 volt × 1 coulomb 
1 Joule : “Is the amount of work done when a charge of one coulomb flows through a 
conductor at a pot. diff. of 1 volt.” 
(c) Name two bigger units of electric work. How are they related to SI unit ? 
Answer: 
Two bigger units of electric work : 
1. Kilo – Joule (kJ) = 10
3
 J 
2. Mega-joule (Mj) = 10
6
 J 
Question 2. 
Derive an expression for electric work connecting : 
(a) Current, resistance and time 
(b) Current, potential difference and time. 
(c) Potential difference, resistance and time. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
https://www.ncertbooksolutions.com
Answer: 
 
 
Question 3. 
State three factors which determine the quantity of heat produced in a conductor. 
Answer: 
Three factors which determine heat produced in a conductor : 
Heat produced = Energy Work done 
W=H=I
2
Rt 
? Three factors are I — current 
R — Resistance of conductor 
t — time for which current flows. 
Question 4. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
https://www.ncertbooksolutions.com
(a) What do you understand by the term electric power ? 
(b) State SI unit of electric power and define it 
(c) Name two bigger units of electric power and their relation with SI unit. 
Answer: 
 
 
Question 5. 
Derive an expression for electric power connecting : 
(a) Current and resistance. 
(b) Current and potential difference. 
(c) Potential difference and resistance. 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
https://www.ncertbooksolutions.com
Answer: 
 
 
 
Question 6. 
(a) What do you understand by term electric energy ? 
(b) Name and define the smallest commercial unit of electric energy. 
(c) Name and define the standard commercial unit of electric energy. 
Answer: 
(a) Electric energy : E = P × t = VIt 
“Electric energy is the product of power and time.” i.e. electric energy consumed by an 
electrical appliance is produced of ‘power rating’ and ‘time’ for which it is used. 
(b) Unit of electric energy ? Joule (J) 
S.I. unit of electric work ? Joule (J) 
1J = 1 volt × 1 coulomb 
1 Joule : “Is the amount of work done when a charge of one coulomb flows through a 
conductor at a pot. diff. of 1 volt.” 
(c) Standard Commercial unit of Electric Energy : Kilo-watt-Hour 1 kwH : “Is the amount 
of electrical energy consumed when an electrical appliance having a power rating of 1 
kilowatt is used for 1 hour.” 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/
https://www.ncertbooksolutions.com
Question 7. 
With respect to electricity, define : 
1. watt hour 
2. watt 
3. kilowatt 
4. kilowatt hour. Amongst the above units, which are the units of : (i) electric energy 
(ii) electric power. 
Answer: 
 
 
 
Question 8. 
How many joules of energy is equal to one kilowatt hour? 
Answer: 
 
 
Downloaded from https://www.ncertbooksolutions.com/
Downloaded from https://www.ncertbooksolutions.com/