Q.No.210: - Why electric current pass through conductors?

Q.No.210: - Why electric current pass through conductors?

Ans: - Because conductors have electrons that are loosely packed with nucleus and become a free electron after getting a small energy. These free electrons conduct electricity.

Q.No. 208: - Why electric current does not conduct through insulators under normal conditions?

Q.No. 208: - Why electric current does not conduct through insulators under normal conditions?

Ans: - Because in insulators electrons orbiting around the nucleus are tightly bound. The free electrons in the insulator are very rare, so that’s why the electric current did not pass through the insulators.

Q.No.207: - Define electric current.

Q.No.207: - Define electric current.

Ans: - Flow of electric charge from high to low potential is called electric current

                                           I    =    Q/t

Where I represents current, Q for charge and t for time.

Q.No.181: - Name two factors which can enhance thermionic emission.

Q.No.181: - Name two factors which can enhance thermionic emission.

Ans: - 1) Temperature

 2) Sun light and heat is used to generate electricity and increase the efficiency of solar power production by more than twice the current levels.

Q.No.179: - A wire lying perpendicular to an external magnetic field carries of a current in the direction shown in the diagram below. In what direction will the wire move due to the resulting magnetic force? (sorry for diagram.)

Q.No.179: - A wire lying perpendicular to an external magnetic field carries of a current in the direction shown in the diagram below. In what direction will the wire move due to the resulting magnetic force? (sorry for diagram.)

Q.No.179: - A wire lying perpendicular to an external magnetic field the magnetic field is along positive x-axis. The wire carrying a current in the direction along positive y-axis. In what direction will the wire move due to the resulting magnetic force?

Ans: - Apply Fleming Left hand rule first finger shows the direction of magnetic field and second finger shows the direction of current and the erected thumb shows the direction of force exerted by magnetic field. So in this case the force will exert in the negative z-axis.

(The direction in the figure below is opposite to that of question that’s why the direction of force will also be opposite i.e., in the downward direction.)

Q.No.178: - What reverses the direction of electric current in the armature coil of D.C. motor?

Q.No.178: - What reverses the direction of electric current in the armature coil of D.C. motor?

Ans: - To reverse the direction of current, the connection to coil is made through an arrangement of brushes and a ring that is split into halves, called a split ring commutator. Brushes which are usually pieces of graphite make contact with the commutator and allow current to flow into the loop. As the loop rotates, so does the commutator. The split ring is arranged so that each half of the commutator changes brushes just as the coil reaches the vertical position. Changing brushes reverse the current in the loop.

Q.No.173: - Suppose you have a coil of wire and a bar magnet. Describe how you could use them to generate an electric current.

Q.No.173: - Suppose you have a coil of wire and a bar magnet. Describe how you could use them to generate an electric current.

Ans: - We will move the bar magnet into and out of the coil and this changing magnetic field will induce emf and electric current.

Q.No.162: - An electrified rod attracts pieces of paper. After a while these pieces fly away! Why?

Q.No.162: - An electrified rod attracts pieces of paper. After a while these pieces fly away! Why?

Ans: - Electrified rod has more number of electrons when we took this rod near to the piece of paper which is neutral the charge from rod shifts to the paper after the transfer of charge the paper get charged and now both have equal number on electrons. Now these electrons exert a repulsive force on each other. That’s why after a while paper pieces fly away.

Q.No.146: - In order to measure current in a circuit why ammeter is always connected in series?

Q.No.146: - In order to measure current in a circuit why ammeter is always connected in series?

Ans: - According to the definition of electric current. Number of charges passing through a point in a unit time is called electric current. So from this definition we can say that electric current associated to the points of the conductor, that’s why we must apply it in series not in parallel. 

Q.No.145: - Two points on an object are at different electric potentials. Does charge necessarily flow between them?

Q.No.145: - Two points on an object are at different electric potentials. Does charge necessarily flow between them?

Ans: - Electric current flow due to the potential difference. If the object is conductor and there is a potential difference occurs between to different points then electric current will flow. But if the object is insulator then no current will flow.

Q.No.142: - Why in conductors charge is transferred by free electrons rather than by positive charges?

Q.No.142: - Why in conductors charge is transferred by free electrons rather than by positive charges?

Ans: - Because electrons are free in conductor and they are in majority. When we apply an external electric field with the help of a battery (source of emf) then these free electrons move from negative to positive terminal of battery. On the other side, positive charges are present in the nucleus of the atom and they are not free to move that’s why electric current is caused by free electrons.