ELECTRICITY -II :BRIEF ANSWERS

ANSWER IN BRIEF

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1. HOW DO WE GET FLOW OF ELECTRONS IN A CONDUCTOR ?
   

   ANS:
   

   
   
   • In an atom the electrons revolving around the nucleus in different orbits are tightly bound to the protons in the nucleus.
     
   • In metals the electrons in the outermost orbit are relatively free to move and are called free electrons.
     
   • These free electrons move randomly in the metal and their net movement in a particular direction is zero.Therefore we do not get current.
     
   • If we provide energy to these free electrons, they move in one direction and we get flow of electrons(current).
     
   • Thus we get current(flow of electrons) by connecting the conductor to a source of energy which creates potential difference across the conductor.
     

   
   

   
   
2. STATE OHM'S LAW AND WRITE ITS FORMULA(EQUATION).
   

   ANS:
   Ohm's Law: The current passing through a conductor is directly proportional to the potential difference(voltage) across the conductor.
   
   Its formula is:
   
         V = I R
   

   Where V = potential difference
   
   I = current in the conductor
   
   R = resistance of the conductor.

   
   

   
   
3. WRITE THE DISADVANTAGES OF SERIES CONNECTION.
   

   ANS:
   The disadvantages of series connection are :
   

   
   
   1. The total resistance in this case is the sum of all resistances.This causes more power loss.
      
   2. The source voltage gets divided among all resistances in series.The equipment either do not work or they work less efficiency.For example if two bulbs of 230V rating are connected in series in a line of 230V then each gets only 115V and gives dim light.
      
   3. If a bulb connected in series with other equipment blows off then it breaks the whole circuit and remaining equipment(like TV, fridge, computer etc.) also stop working.
      

   
   

   
   
4. WRITE ADVANTAGES OF PARALLEL CONNECTION.
   

   ANS:
   The advantages of parallel connection are:
   

   
   
   1. For parallel connection, the voltage drop across each resistor is same.Since the voltage drop is uniform and is equal to that of the source,an equipment like bulb does not glow dim even if there are more appliances .
      
   2. If an equipment or bulb fails to work, the remaining equipment continue to work as the current is not disrupted in remaining circuit.
      
   3. As the equivalent resistance of the circuit is smaller than the smallest resistance of the circuit, there is minimum power loss.
      

   
   

   
   
5. EXPLAIN THE CAUSE OF RESISTANCE IN A CONDUCTOR AND DIFFERENTIATE BETWEEN CONDUCTORS AND INSULATORS
   

   ANS:
   

   
   
   • Electrical resistance is a property of the conducting wire.
     
   • When electrons try to move within the conducting wire, their movement is opposed by the atoms and molecules of the conductor.
     
   • The collision of electrons with atoms(molecules) gives rise to resistance to the movement of electrons.
     
   • Metallic elements are good conductors because of free electrons in them.These free electrons overcome the resistance and produce current.
     
   • Materials like plastic, wood, rubber,etc. are insulators(bad conductors) as they do not have free electrons to produce current.
     

   
   

   
   
6. EXPLAIN : ELECTRICAL ENERGY
   

   ANS:
   

   
   
   • To maintain the flow of charge(current), a battery has to do work continuously on the charge.
     
   • This work done on charge is converted into electrical energy.
     
   • If
     
     W = work done by the battery
     
     V = voltage of battery
     
     Q = electric charge
     
     I = current
     
     R = resistance
     
     t = time
     
     then we have,
     
     W = V x Q
     
     ∴ W = V x I x t        [as Q = I x t]
     
     ∴ W = I² x R x t        [as V = I x R]
     
     Thus, W is the energy consumed if the current(I) flows through resistance(R) for time (t).The unit of electrical energy is joule(J).
     

   
   

   
   
7. EXPLAIN : ELECTRICAL POWER
   

   ANS:
   

   
   
   • The rate at which the electrical energy is consumed is known as electrical power.In other words electrical energy consumed per unit time is called power.
     
     
   • If P is electrical power, then
     
     P = W/t
     
     ∴ P = (I² x R x t)/t        [as W = I² x R x t]
     
     ∴ P = I² x R
     
     or P = V x I        [as I x R = V]
     
     The unit of power is watt.
     
     
   • When 1 ampere current passes through a circuit having voltage of 1 V, the power is called 1 watt.
     

   
   

   
   
8. WHAT IS ELECTROLYSIS ? WRITE FARADAY'S LAWS OF ELECTROLYSIS
   

   ANS:
   
   Electrolysis is the process of separation of ions of a subsatnce with the help of electric current.
   
   Faraday's Laws of Electrolysis
   

   
   
   1. The mass of the substance deposited on cathode is proportional to the charge passing through the electrolyte.
      
   2. For a given amount of charge passed, the masses of different elements deposited on the cathode are in proportion to their chemical equivalents.
      

   
   

   
   
9. GIVE REASON : ONE SHOULD NOT TOUCH ELECTRICAL SWITCH WITH WET HANDS.
   

   ANS:Pure water is bad conductor of electricity but the tap water used by us contains dissolved impurities. Due to this water becomes good conductor of electricity. If we touch a switch with wet hands, there is a chance that current will flow through our body due to water on our hands and this may give us an electric shock and harm us.
   



10. STATE THE ADVANTAGES OF HEATING EFFECT OF CURRENT IN DAILY LIFE.
    

    ANS:

    
    
    • Domestic appliances such as electric heater, electric iron, electric lamp, toaster, etc. use heating effect of electric current.
    • Fuse is a safety device consisting of a low melting point wire. When current increases abruptly due to some reason, fuse melts and breaks the circuit. It thus protects us and the costly appliances from being damaged.
      

    
    



11. DISTINGUISH BETWEEN AMMETER AND VOLTMETER.
    

    ANS: