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A parallel plate air capacitor has a capacitance C. When it is half filled as show in figure with a dielectric constant $K=5$, the percentage increase in the capacitance is ________.
Step 1: Initial Capacitance
The initial capacitance of the parallel plate air capacitor is given by:
Step 2: Equivalent Capacitance with Dielectric
When a dielectric of constant $K = 5$ fills half the distance ($\frac{d}{2}$), the system behaves as two capacitors connected in series:
-
Air-filled portion ($C_1$):
$$C_1 = \frac{\varepsilon_0 A}{\frac{d}{2}} = \frac{2\varepsilon_0 A}{d} = 2C$$ -
Dielectric-filled portion ($C_2$):
$$C_2 = \frac{K \varepsilon_0 A}{\frac{d}{2}} = \frac{5 \cdot 2\varepsilon_0 A}{d} = 10C$$
Using the equivalent series capacitance formula:
Step 3: Percentage Increase
For the reaction $2\text{C}_{57}\text{H}_{110}\text{O}_6(s) + 163\ \text{O}_2(g) \to 114\ \text{CO}_2(g) + 110\ \text{H}_2\text{O}(l)$, find the mass of water produced from 445 g of C$_{57}$H$_{110}$O$_6$.
Molar mass of C$_{57}$H$_{110}$O$_6$: $57(12)+110(1)+6(16)=684+110+96=890\ \text{g mol}^{-1}$
Moles of C$_{57}$H$_{110}$O$_6 = \dfrac{445}{890} = 0.5\ \text{mol}$
From stoichiometry: 2 mol fat → 110 mol H$_2$O
So 0.5 mol fat → $\dfrac{110 \times 0.5}{2} = 27.5\ \text{mol H}_2\text{O}$
Mass of H$_2$O $= 27.5 \times 18 = \mathbf{495\ \text{g}}$
Tracing the folds:
- Fold 1 (diagonal): The paper is now a triangle. The folded corner = centre of original square.
- Fold 2 (triangle halved): The apex is still at the centre of the original square.
Punching at the folded corner (intersection of all folds = exact centre) means the punch goes through all 4 layers. But since the hole is at the centre, when unfolded it reveals 1 hole at the centre of the square — the layers were all stacked at that single point.
If the punch were at a non-fold point, you'd get 4 holes. But the apex/folded corner is a single geometric point — 1 hole appears.
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