Physics 3rd year exam 4

When a potential difference of (6 volts) is applied on a conductor there is a current of intensity (3A) passes, and if p.d. is changed to be (8 volts), then the current intensity becomes (4A), so this resistance ...............................?

• Obeys ohm's law

• doesn't obey ohm's law

• No correct answer

A wire is folded (reshaped) so that it's diameter is doubled. It's resistance will be ................................

• The same

• Decrease 16 times

• doubled

• decreases to quarter

A metallic rod is reshaped such that it's length is increased three times, it's electric resistance would increase .....................................?

• Three times

• Six times

• Nine times

• Twelve times

The resistance of resistor (1) is twice the resistance of resistor (2). The two are connected in parallel and a potential difference is maintained across the combination. Then ........................................?

• The current in (1) is twice that in (2)

• The potential difference across (1) is twice that across (2)

• The potential difference across (1) is half that across (2)

• The current in (1) is half that in (2)

In the circuit, the galvanometer (G) shows zero deflection. If the two batteries have negligible internal resistance, the value of the resistor (R) will be ......................................?

• Close

  Open

• Open

  Close

• Close

  Close

• Open

  Open

• 
• 
• 
• 

In the following circuit. Wire carry a current placed tangent to ring carry a current, detect direction of current and it's value that must pass in ring to make total magnetic flux at center = zero. Then calculate total magnetic flux at this center if current reversed in this ring .....................................?

• (6.28 A) clockwise

• (6.28 A) counter clockwise

• (2 A) clockwise

• (2 A) counter clockwise

A circular coil carries an electric current that produces a magnetic field of density (B) at the center of the coil. When the electric current intensity is increased to the double and the radius of the coil is increased to the double with keeping the same number of turns, then the magnetic flux density at the center of the coil equals .....................................?

• B

• 2B

• B/2

• 2/B