Electric Circuits

What is the resistance of a copper wire having a diameter of 10 millimeter and a length 10 meters. The resistivity is 1.72 x 10 ^8 ohm-meter.

• 1.92 milliohm

• 2.19 milliohm

• 1.29 milliohm

• 2.91 milliohm

A piece of wire has a resistance of 0.5 ohm. The length is doubled and the area is increased four times. What is its resistance?

• 2.5 ohm

• 0.52 ohm

• 5.2 ohm

• 0.25 ohm

A wire measuring 1.5 cubic meter has a resistance of 0.955 micro-ohm at 20 degree Celcius; its length is 1.5 meters and an area of 1 square meters. Calculate the resistance of this wire at 20 degree Celcius if the length is changed to 150 meters and its area to 450 square centimeter.

• 2.12 milli-ohm

• 1.21 milli-ohm

• 1.12 milli-ohm

• 2.11 milli-ohm

A conductor has a resistance of 7 ohm at 0 degree Celsius. At 20 degree Celsius, the resistance has become 7.5 ohms. Calculate the temperature coefficient of the conductor at 20 degree Celsius.

• 0.0333 per degree Celsius

• 0.000333 per degree Celsius

• 0.00333 per degree Celsius

• 0.333 per degree Celsius

A 1 meter rod of 2 centimeter diameter is drawn until its resistance is 100 times the initial resistance. Its length afterwards is?

• 12.5 meters

• 5 meters

• 10 meters

• 100 meters

The substation bus bar is made up of 2 inches round copper bars 20 feet long. What is the resistance of each bar if the resistivity is 1.724 x 10^-6 ohm centimeter?

• 5.185 x 10^-5 ohms

• 7.21 x 10^-6 ohms

• 13.8 x 10^-6 ohms

• 2.96 x 10^-6 ohms

The resistance of a wire is 126.48 ohm at 100 degree Celsius and 100 ohms at 30 degree Celsius. Determine the temperature coefficient of copper at 0 degree Celsius.

• 0.00615 per degree Celsius

• 0.00427 per degree Celsius

• 0.0256 per degree Celsius

• 0.0356 per degree Celsius

Solve the problem using Kirchhoff's Laws. Two batteries are connected in parallel supplying a common load of 2 ohms. Batteries A and B have an open circuit voltages and internal resistances of 10 V, 2 ohms; and 8 V, 2 ohms respectively. Calculate the load current.

• 3 amperes

• 2 amperes

• 4 amperes

• 5 amperes

A resistance R is connected across two batteries A and B connected in parallel. The open circuit emfs and internal resistances of the batteries are 12 V, 2 ohms and 8 V, 1 ohm, respectively. Determine the ohmic value of R if the power absorbed by R is 7.656 watts.

• 12 ohms

• 8 ohms

• 10 ohms

• 9 ohms

In Manila, the LRT runs between Gil Puyat Station and Tayuman Station, which is 4 kilometers apart and maintains voltages of 420 volts and 410 volts respectively. The resistance of go and return is 0.05 ohm per kilometer. The train draws a constant current of 300 amperes while in motion. What are the currents supplied by the two stations if the train is at the distance of minimum potential?

• 183 A, 117 A

• 175 A, 125 A

• 164 A, 136 A

• 172 A, 128 A