Reference no: EM132313547

Questions:

[1] An empty rechargeable battery of an electric forklift is charged by a constant current of 16 A.
• Draw the underlying circuit diagram.
• How large is the total charge of the battery after 5 hours?
• How much unit charges have flown into the battery?
• How large is the current density in the copper cable when it has a diameter of 2 mm?
• What happens in general, if the current density increases?

• How large is the drift velocity of the electrons in the copper cable during charging?

[2] Assume that the charging process of the battery has an efficiency of 80%.

• How long would you have to charge the battery in order to reach a complete charge if a charging process with 100% efficiency would last 5 hours?
• What happens to the energy getting lost?

(3) In your household you plug the following electrical devices into your wall outlets:
(1) a vacuum cleaner with 800 Wi (2) a hairdryer with 1 200 W and (3) a heater with 2 kW.
• Draw the corresponding electrical diagram of the network.
• How much current do the individual electric devices consume? Assume a constant voltage of 230 V across the wall outlet.
• How large are the resistances of the three devices?
• Would a fuse designed for 16 A being adequate to allow the operation of all three devices at the same time?
• Which devices could be operated at the same time using the 16 A fuse?

[4] An overhead powedine made of aluminium from the transformer station to an industrial facility has a length of 5 km and a diameter of 1 cm.
• How large is its resistance of one line at 20t?
• How large is its conductance of one line at 20°C?
• How large is the resistance if the powerline heats up to 60°C?

[5] The overhead powerline from the previous question is fed with 400 V and supplies an industrial equipment using 10 kW of electrical power. Assume a temperature of 20°C for the powerline.

• Draw an equivalent circuit diagram.
• How much current flows through the line?
• How much voltage and how much power is dropped along the line?
• What does this mean for the equipment to be supplied?
• How much electric work (or energy) is consumed by the emipment in 24 hours of continuous operation?

[6] In an electronic circuit you need to implement a resistor with a value of 2,2 kΩ.

• You already have one resistor of 1,0 k0. Which value must an additional resistor have that you place in series in order to get the desired total value?
• You already have one resistor of 4,7 ku. Which value must an additional resistor have that you place in parallel in order to get the desired total value?
• How will the resulting values in general be, when you connect resistors in series and in parallel?

[7] High performance overhead power transmission lines are operated at voltages up to 1,1 MV.
• How large is the electrical field strength in 5 meters?
• Which minimum distance need to be kept in order not to initiate a spark?

Assume a dielectric breakdown field strength of air of about 3 x 10. Vim.