Capacitors
1 A
capacitor has a charge of 20 μC (microcoulomb) when a p.d. of 200 V is applied
to it. Calculate the capacitance of the capacitor. 1x10-7F
What is the
charge on the capacitor if a battery of 40 V is connected?
4 x10-6C
2 Define capacitance, microfarad. Calculate the p.d. across a 2 μF capacitor if it has a charge of 80 μC. 40V Calculate the new p.d. if the capacitor is then connected to an uncharged capacitor of 4 μF. 13.3V What is the charge on each capacitor in this case? 2.7 x10-5 C, 5.3 x10-5 C
3 Calculate the combined capacitance of (i) 2 μF and 3 μF capacitor in series, 1.2 μF (ii) a 4 μF capacitor in series with a parallel arrangement of a 3 μF and 2 μF capacitor. 2.2 μF Prove from first principles the formula 4 for the combined capacitance of two capacitors in series and in parallel.
4 A capacitor of 2 μF is charged by a 100 V battery. Calculate the energy in the capacitor. 1 x10-2 J If the capacitor is disconnected from the battery and then connected to a 6 μF uncharged capacitor, find the new energy in each capacitor 6.3 x10-4 J, 1.9 x10-3 J. Account for the loss in energy which has occurred. Heat lost as current passes through external in circuit, (resistance of wires)
2 Define capacitance, microfarad. Calculate the p.d. across a 2 μF capacitor if it has a charge of 80 μC. 40V Calculate the new p.d. if the capacitor is then connected to an uncharged capacitor of 4 μF. 13.3V What is the charge on each capacitor in this case? 2.7 x10-5 C, 5.3 x10-5 C
3 Calculate the combined capacitance of (i) 2 μF and 3 μF capacitor in series, 1.2 μF (ii) a 4 μF capacitor in series with a parallel arrangement of a 3 μF and 2 μF capacitor. 2.2 μF Prove from first principles the formula 4 for the combined capacitance of two capacitors in series and in parallel.
4 A capacitor of 2 μF is charged by a 100 V battery. Calculate the energy in the capacitor. 1 x10-2 J If the capacitor is disconnected from the battery and then connected to a 6 μF uncharged capacitor, find the new energy in each capacitor 6.3 x10-4 J, 1.9 x10-3 J. Account for the loss in energy which has occurred. Heat lost as current passes through external in circuit, (resistance of wires)
|
6 Two capacitors of 25 μF and 100 μF respectively are joined in series with a d.c. supply of 6.0 V. Fig 3 (i) What is the charge on each capacitor and the p.d. across each? 1.2 x 10-4 C, 4.8V, 1.2V
The supply is now disconnected without affecting the charge on each capacitor. Their two positive plates, and their two negative plates, are then connected together Fig. 3 (ii). Calculate (i) the common p.d. of the capacitors, 1.92 V(ii) the loss in energy of the two capacitors. 1.3 x10-4 J. How is this loss of energy accounted for?
7 A 100 V supply is connected to a 4 μF capacitor in series with a 2 MΩ (2 million ohms) resistor. Find (i) the current I at the instant of switching on the supply 5 x10-5A, (ii) the final charge on the capacitor4 x10-4C, (iii) the time taken to charge the capacitor assuming the mean value of the current during flow of charge is I/2. 16s (I do know of the approximation of 5RC, but you have to use the information in the question)
8 A 25 μF capacitor, previously charged by a p.d. of 10 V, is discharged through a 2 MΩ(2 x 106Ω) resistor. What is: (i) the initial charge on the capacitor 2.5 x10-4C (ii) the initial current? 5 x10-6 A
