Electricity || Class 9 Science Notes

Electricity

1. Short answer type questions.   

a. Define resistance.   

=  Resistance is the property of a captain by virtue of which it opposes the inflow of electric current.  

b. Define electric current?   

=  Electric current is the rate of inflow of electric charge.   

c. What's 1Ω resistance?  

 =  If a current of 1A through a captain maintains a pd of 1V across its ends,  also it's called 1Ω resistance.   

d. State Ohm's law?   

→ The electric current quilting through a captain is directly commensurable to the implicit difference acme its ends at constant physical conditions known as Ohm's law.   

e. Define electric power?   

=  The rate of conversion of electrical energy into non-electrical energy by an electrical device in a unrestricted circuit is called electric power.   

f. What's the unit of electric consumption?   

→ The unit of electric consumption is kWh or unit.   

g. What does a dry cell of 1.5 V indicate?   

=  A dry cell of 1.5 V indicate that electric inventories 1.5 J energy to produce 1.5 C charge.   

h. Give the relation of resistance of  line with its length and consistence.   

=  The relation of resistance of  line with its length and consistence is resistance is directly commensurable to the length of the conducting  line and it's equally commensurable to the consistence of the conducting  line.   

i. What change in the resistance of a captain occurs with change in its temperature?   

→ The resistance of a captain increase when change in the resistance of a captain with increase or  drop change in its temperature.   

j. In which combination  outfit of different capacities be connected?   

=  In  parallel combination, the  outfit of different capacities be connected.   

k. A  invariant resistance  line is stretched till its length becomes four times. Does its resistance increase  drop?   

→ Its resistance increase.   

2. Long answer type questions.   

a. Derive the relation of 1kWh with joule.   

= The relation of 1kWh with joule is given below :-  

1kWh =  1000 W x 36003(- 1kW =  1000W)   

or, 1kWh =  1000J/ s x 3600s(- 1W =  1J/ s and 1h =  60x60s)  

 therefore, 1kWh = 3.6 x 106 J   

b. Describe emf and pd with suitable  illustration.   

→ Electromotive force( emf) is the  quantum of electrical energy converted into electrical an electric source to inflow unit charge in a circuit. partner Electric cell.   

=  The  quantum of energy converted from electrical to non-electrical by the electric  cargo when one unit charge inflow in it's called implicit difference( pd) ex   decide the relation V =  IxR.   Then,' R' is electrical resistance of the captain, which is used as constant. If' I' is the electric current through a  line and' V' is the id across its ends.   I ∝ V   or, V ∝ I  - V =  RI   

c. Mention the factors of resistance and their  goods.   

=  The factors of resistance are:-

i. Materials

ii. length   

iii. consistence   

iv. temperature   

= The  goods of resistance are:-   

i. It increase heating of  line.   

ii. It disturbs the inflow of charged electrons.     

e. Why can not we connect electrical  bias of  veritably different capacities in a series combination?   

→ We can not connect electrical  bias of  veritably different capacities in a series combination because if there will be a short circuit in one of the appliance which led to break in the circuit will beget the working of other appliance connected in the Series.   

f. What are the advantages of a  resemblant combination over a series combination?   

→ The advantages of a  resemblant combination over a series combination are:-   

i. Each appliance gets the full voltage.   

ii. If one appliance is switched on others aren't affected.   

iii. The  resemblant circuit divides the current through the appliances.   

g. In which combination do all the connected  lights emit  analogous light indeed allowed one of them is removed from the circuit? Explain.   

=  In  parallel combination all the connected  lights emit  analogous light indeed allowed of them is removed from the circuit. For  illustration. A bulb have negative and positive point and other bulbs have also same points if we connect all the bulbs directly to the cell all the bulbs emit  analogous light and indeed allowed one of them is removed from he circuit, other bulbs have no change.  

h. In which combination of loads does the brighten of  lights increase if the number of  lights reduced in the circuit? Explain.   

= In series combination of loads, the brighten of  lights increase of the number of  lights is reduced in the circuit. For ex A cell have1.5 V and three bulbs connected to the cell laterally also one bulb absorbs0.5 V so, three bulbs dos1.5 V if one bulbs removed  also two bulbs, each bulbs absorbed0.7.5 V and brilliance of bulb increase.  

i. For what purpose do we use the heating effect of electric current?   

=  In order to run heater, Rice cooker, Toster, Kettle, Gyser, etc for heating water we use the heating effect of electric current.   

3. Give reasons.   

a. Ammeters are connected in series.   

→ Because they've a low resistance and can measure the current of a circuit only when total electric current is passed though the device. It's possible only series combination.   

b. kWh is used to measure electric consumption.   

→ Because 'J' won't be accessible to read, write and calculate the electric bill of a month.   

c. Voltmeters are connected in a  parallel combination.   

⇒ Because they've more resistance to measure the difference in implicit pressure between two outstations the device has to be connected between the outstations in parallel.  

d. The tungsten  hair is made long.   

→ Because due to high melting point and resistivity.   

e. Nichrome  line is used to make a heating element.  

=  Because it offer the  veritably large resistance.   

f. Electrical device of a different power can not be used in a series combination.   

→ Because if there will be a short circuit in one of the appliances which led to break in the circuit will beget the working of other appliances connected.