Physics 3rd year final exam 2

Four electric resistances as in the figure, the pointer of ohmmeter reads the same reading when the device is connected between the two points ...........................?

• "c" and "b" or

  "b" and "d"

• "a" and "c" or

  "a" and "d"

• "a" and "c" or

  "b" and "d"

• "a" and "d or

  "c" and "d"

According to the opposite circuit , which of the following represents what will happen to the reading of the voltmeter by changing the value of resistance which is taken from rheostat ?

• A

• B

• C

• D

• A

• B

• C

• D

• A

• B

• C

• D

• 8 V

• 10 V

• 9 V

• 12 V

The opposite graph represents the relation between the resistance (R) of two groups of wires "X" and "Y" (each group is made of a different material) and the reciprocal of cross-sectional area (1/A) at the same temperature. Given that the length of each wire is (1 m) . Which of the following choices is correct ?

• A

• B

• C

• D

Two parallel long wires (X) and (Y) the normal distance between them is (0.5 m) , the two wires carrying currents pass in the same direction , the value of the current in wire (X) is (I) and that of wire (Y) is (3I) , so that the position of the neutral point is at a distance ............................?

• 0.125 m from wire Y

• 0.25 m from wire Y

• 0.125 m from wire X

• 0.625 m from wire X

A solenoid made of insulated copper wire carrying an electric current (I) , and the magnetic flux density along its axis is (B) , if the turns are displaced uniformly away from each other, so the magnetic flux density along its axis is decreased to (B/4) . If we have to increase the current intensity by (3 A) to return the value of magnetic flux density to its initial value (B) , then the current intensity (I) is ...........................?

• 1 A

• 2 A

• 3 A

• 4 A