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Ferric oxide crystallises in a hexagonal close-packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide.
Ans: Let the number of oxide $\left(\mathrm{O}^{2-}\right)$ ions be $\mathrm{x}$. So, number of octahedral voids $=x$ It is given that two out of every three octahedral holes are occupied by ferric...
If 
is doped with 
of 
, what is the concentration of cation vacancies?
Ans: It is given that $\mathrm{NaCl}$ is doped with $10^{3} \mathrm{~mol} \%$ of $\mathrm{SrCl}_{2}$. This means that $100 \mathrm{~mol}$ of $\mathrm{NaCl}$ is doped with $10^{3} \mathrm{~mol}$ of...
In an A.C. circuit having resistance and capacitance :
A emf leads ahead of the current
B current lags behind the emf
c both the current and emf are in phase
D current leads ahead of the emf
Correct option is D current leads ahead of the emf $\mathrm{D}$ In circuits with primary capacitive loads, currently leads to the voltage. This is because the current must flow first to the two...
A parallel-plate air condenser of plate area A and separation d is charged to potential V and then the battery is removed. Now a slab of dielectric constant k is introduced between the plates. If Q, E, and W denote respectively the magnitude of the charge on each plate, the electric field between the plates (after the introduction of the dielectric slab) and work done on the system in the process of introducing the slab, then
A 
B 
c 
Correct option is A $\mathrm{W}=\frac{\varepsilon_{0} \mathrm{~A} \mathrm{~V} \mathrm{~h}^{2}}{2 \mathrm{~d}}(1-1 / \mathrm{k})$ C $Q=\frac{\varepsilon_{0} A V}{d}$ D $\quad E=\frac{V}{k d}$ As...
Aluminium crystallises in a cubic close-packed structure. Its metallic radius is 
.
(i) What is the length of the side of the unit cell? Ans: For cubic close-packed structure: $$ \begin{array}{l} \mathrm{a}=2 \sqrt{2} \mathrm{r} \\ \Rightarrow 2 \sqrt{2}=125 \mathrm{pm} \\ =353.55...
A parallel plate capacitor with a dielectric slab of dielectric constant 3, filling the space between the plates, is charged to a potential V. The battery is then disconnected and the dielectric slab is withdrawn. It is then replaced by another dielectric slab of dielectric constant 2. If the energies stored in the capacitor before and after the dielectric slab is changed are 
and 
, then 
is:
A 
B 
c 
D 
Correct option is B $\frac{2}{3}$ Let the charge stored by a capacitor with dielectric constant 3 be $Q$. Thus energy stored be $\frac{\mathrm{Q}^{2}}{2 \mathrm{C}_{1}}$ Since the charge remains the...
A parallel plate capacitor is first charged and then isolated, and a dielectric slab is introduced between the plates. The quantity that remains unchanged is:
A charge Q
B potential V
C capacity C
D energy U
The correct option is (A) charge Q When the capacitor is kept at a voltage, it gains charge. Now when the system is isolated, the charge present on the capacitor cannot change because of the law of...
If is doped with of , what is the concentration of cation vacancies?
Ans: It is given that $\mathrm{NaCl}$ is doped with $10^{3} \mathrm{~mol} \%$ of $\mathrm{SrCl}_{2}$. This means that $100 \mathrm{~mol}$ of $\mathrm{NaCl}$ is doped with $10^{3} \mathrm{~mol}$ of...
When a dielectric slab is introduced between the two plates of the condenser then it’s capacity
A remains constant
B increases
C decreases
D may increase or decrease depending on the material of the dielectric slab
$\mathrm{~ O ~ W e i s c o d i s ~ T o p}$ Correct option is B increases As the dielectric slab is introduced there is some charge distribution in the slab and because of this, the electric field...
Aluminium crystallises in a cubic close-packed structure. Its metallic radius is .
(i) What is the length of the side of the unit cell? Ans: For cubic close-packed structure: $$ \begin{array}{l} \mathrm{a}=2 \sqrt{2} \mathrm{r} \\ \Rightarrow 2 \sqrt{2}=125 \mathrm{pm} \\ =353.55...
Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show cleavage property?
Ans: As isotropic solid has the same value of physical properties when measured along different directions. Therefore, the given solid, having the same value of refractive index along all...
In the LCR circuit if resistance increases, then the quality factor
A) increases finitely
B decreases finitely
C remains constant
D None of these
The correct option is B decreases finitely Quality factor $Q$ is given by: $$ \mathrm{Q}=\frac{\omega_{0} \mathrm{~L}}{\mathrm{R}} $$ Thus, as $\mathrm{R}$ increases Q definitely decreases.