MODULE V Electrical engineering - Basics Page 11

1.7 Exercises

1. Determine the resistance of the field winding of a circulation pump if it consumes a current of 0,5A with a voltage of 230V.
   
   
2. A heating rod takes consumes a current of 6,1A with a voltage of 400V. Calculate the resistance of the heating rod.
   
   
3. The electric current that is flowing through the coil of an ignition transformer has to be determined. Its resistance is 2,5k, the applied voltage is 230V.
   
   
4. Determine the exact electrical voltage that is applied to an "NTC feeler" under the following conditions:
   a) 25°C, 0,930k
   b) 32°C, 780
   The signal current is constant in both cases with 1,5mA.
   
   
5. Determine the conductor resistance of a 20m long copper cable with a cross section of 0,04cm2, the temperature is 20°C.
   
   
6. Determine how long an aluminium cable can maximally be if its cross section is 0,025cm2 and its conductor resistance should maximally be 0,0028k at a temperature of 20°C.
   
   
7. The electrical arc welding resistance is 1/3. Determine the amperage if the voltage is 25V.
   
   
8. A coil through which direct current is flowing consists of 100m of copper wire whose cross section is 0,036mm2. Calculate the necessary size of the dropping/in series connected resistor if the total resistance should be 100.
   
   
9. The resistivity of a part made of an unknown material has to be determined. The length of the part is 2cm, its cross section is 4mm2 and a resistance of 10 had been determined in a measurement.