Capacitors in parallel
Capacitors - OCR A-Level Physics
Worked Example
Two capacitors of 20 \mu F and 30 \mu F are connected in parallel across a 6.0 V supply. Calculate: (a) the total capacitanceThe chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). stored per unit potential difference across a capacitor. Measured in farads (F)., (b) the total chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). stored, (c) the total energyThe capacity to do work. Measured in joules (J). stored.
Show Solution
1
(a) In parallel
$C_{\text{total}} = C_1 + C_2 = 20 + 30 = 50 \mu\text{F} = 50 \times 10^{-6} \text{ F}$
2
$(b) Q = CV = 50 \times 10^{-6} \times 6.0 = 3.0 \times 10^{-4} \text{ C} = 300 \mu\text{C}$
3
$(c) E = \frac{1}{2}CV^2 = \frac{1}{2} \times 50 \times 10^{-6} \times 6.0^2 = 9.0 \times 10^{-4} \text{ J} = 0.90 \text{ mJ}$
Answer
$(a) $50 \mu$F, (b) $300 \mu$C, (c) 0.90 mJ$