ACTIVITY 2
1. The diagram shows a DC resistor network. The network is supplied by a 12 V battery.
. The diagram shows a DC resistor network. The network is supplied by a 12 V battery
Using the information in the network diagram, calculate:
(a) the current flowing through resistor R5
(b) the overall power dissipated in the network.
2. A transformer is used to provide an AC supply to a piece of portable equipment.
A transformer is used to provide an AC supply to a piece of portable equipment
(a) Calculate the peak value of the input supply.
(b) Calculate the output voltage from the transformer and then draw a waveform to represent the output voltage over two cycles.
You should indicate the amplitude and the time period on the waveform.
(c) A technician checks the operation of the transformer. The calculations show that the transformer is 93% efficient. Use this information to calculate the actual output voltage from the secondary coil.
3. An electrical engineer has connected a coil to a 120 V AC supply at a frequency of 50 Hz.
An electrical engineer has connected a coil to a 120 V AC supply at a frequency of 50 Hz
0.75 C of charge passes through the coil in 5 minutes.
(a) Calculate the current passing through the coil.
The coil has an internal resistance of 68 ohms.
(b) Calculate the inductance of the coil.
The diagram shows a fully charged capacitor that is discharged through the resistor when the switch is closed.
power and energy assessment 3
(c) Calculate the time constant of the capacitor.
When the capacitor is fully charged and t = 0, the voltage across it is 16 V.
(d) Calculate the voltage across the capacitor after 12 seconds.
4. The diagram shows a resistor network with two power supplies.
The diagram shows a resistor network with two power supplies.
V1 is supplied from a variable power supply that is supplied with a current of 1.1 amps.
(a) Calculate the power drawn by the power supply.
(b) Calculate the current flowing through resistor R3.
(c) The supply voltage V2 is increased to 15 V. Explain how this would affect the current flowing through resistor R3.
