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Current Electricity

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Q.

Column 1 has some conductor across which battery is connected as shown. Variation of resistivity ρ is also indicated. Which of the quantities in column 2 remain constant throughout the volume of conductor.

                  Column 1

                Column 2

  (A)

       

  (p)

   Magnitude of electric field

(B)

 

(q)

Magnitude of current density

 (C)

        

  (r)

  Electric power dissipated per     unit volume

 (D)

       

  (s)

  Drift speed of free electron

 

Q.

In column-1 certain graph(s) are shown which depict the situation shown in column-2.

                  Column 1

                  Column 2

(A)

 n   

 

(p)

             

Distance of soldier from left end = x.

Reading of galvanometer = y

(B)

       

 

(q)

               

Uniformly charged sphere, distance from centre = x,

Potential = y

 (C)

  

 (r)

               

Kinetic energy of a projectile = y

height  from ground = x

 (D)

        

 

  (s)

Velocity of a particle executing SHM = x,

Displacement from mean position = y

              

  (t)

Heat is extracted from a solid at a constant rate. The temperature of the solid = y, time elapsed = x

 

Q.

On a parallel plate air capacitor of capacitance  having plate separation dfollowing steps are performed in the order as given in column 1.

(a) Capacitor is charged by connecting it across a battery of EMF 

(b) Dielectric of dielectric constant k and thickness d is inserted

(c) Capacitor is disconnected from battery

(d) Separation between plates is doubled

 

                   Column 1

      (Steps performed in order)

                 Column 2

    Final value of Quantity  (Symbols have usual meaning)

 (A)

  (a) → (d) → (c) → (b)

  (p)

       

 (B)

 (d) → (a) → (c) → (b)

 (q)

       

 (C)

 (b) → (a) → (c) → (d)

 (r)

      

 (D)

 (a) → (b) → (d) → (c)

 (s)

     

Q.

In the given circuit, initially capacitor has some charge, the switch is closed at t = 0.

                                         

                   Column 1

                 Column 2

 (A)

 Charge v/s time

 (p)

               

 (B)

 Current v/s time

 (q)

              

 (C)

 Charge v/s current

 (r)

            

 (D)

 Energy stored in capacitor  v/s time

 (s)

            

 

Q. If we rubb plastic comb with our hair ,the comb gets negative charge and then when we place same negative charge comb with paper , the negative charge of comb gets attracted with positive charge of papar and the paper's positve charge repel to other side . so my question is that why the negative and postive charge of paper didn't gets attracted towards each other?

they get attracted at atomic level

Q. While calculating the resistance of a wire with radius r and length l,why do we take the cross sectional area of the wire πr^2,rather than the total surface area of the cylindrical wire 2πr(r+l). The resistance of the wire is asked ,so shouldn't we take the total area of wire.but then why are we taking the cross sectional area?

electrons move along the length of wire , so the area through which they are passing will be the cross sectional area , therefore we take the area of circle

Q. In a metal conductor the metal ions do not flow because of their mass or because or because of their mettalic bond?

they have minimum mobility due to strong metaillic bonds

Q. If current flows in circuit consist of resistance, then it should be decreased because of resistance but In calculations we take same current after resistance and as before resistance . So why it does not decreased and remain same?

It is decreased when we do practically but in numerical or in books it will not shown due to some minor decrement . Ptactically and numerical value are always different.

Q. Trick to analyse Wheatstone bridge?

When the bridge is fully balanced, the right side resistors identical to the left side resistors (R1=R3, and R2=Rx), the voltage across the bridge is zero. However, with a small change in resistance on one of the resistors, and the bridge becomes unbalanced, and a voltage difference appears.

you hav to check in the circuit for the whaetstone bridge and then compare the resistances.