List of practice Questions

Answer the following questions:

(a)

1. What is a test cross? How can we find out the zygosity of a plant by the use of test cross? 
2. Why are human females rarely haemophilic? Explain with the help of a cross. Under what conditions can a haemophilic female be born? How do haemophilic patients suffer? 

OR 
(b) Name the two events ‘a’ and ‘c’ shown in the diagram below. 

 

1. Mention where in the cell these events take place. 
2. Explain the changes taking place during event ‘b’ and mention why these are needed.

Study the table given below showing the relationship between organism, its trophic level and kind of food chain it belongs to.

Read the following paragraphs and answer the questions that follow:
A capacitor is a system of two conductors separated by an insulator. In practice, the two conductors have charges \( Q \) and \( -Q \) with a potential difference \( V = V_1 - V_2 \) between them. The ratio \( \frac{Q}{V} \) is a constant, denoted by \( C \), and is called the capacitance of the capacitor. It is independent of \( Q \) or \( V \). It depends only on the geometrical configuration (shape, size, separation) of the two conductors and the medium separating the conductors.
When a parallel plate capacitor is charged, the electric field \( E_0 \) is localized between the plates and is uniform throughout. When a slab of a dielectric is inserted between the charged plates (charge density \( \sigma \)), the dielectric is polarized by the field. Consequently, opposite charges appear on the faces of the slab, near the plates, with surface charge density of magnitude \( \sigma_p \). For a linear dielectric, \( \sigma_p \) is proportional to \( E_0 \). Introduction of a dielectric changes the electric field, and hence, the capacitance of a capacitor, and hence, the energy stored in the capacitor. Like resistors, capacitors can also be arranged in series or in parallel or in a combination of series and parallel.

Extrinsic semiconductors are made by doping pure or intrinsic semiconductors with suitable impurity. There are two types of dopants used in doping, Si or Ge, and using them p-type and n-type semiconductors can be obtained. A p-n junction is the basic building block of many semiconductor devices. Two important processes occur during the formation of a p-n junction: diffusion and drift. When such a junction is formed, a ’depletion layer’ is created consisting of immobile ion-cores. This is responsible for a junction potential barrier. The width of a depletion layer and the height of potential barrier changes when a junction is forward-biased or reverse-biased. A semiconductor diode is basically a p-n junction with metallic contacts provided at the ends for application of an external voltage. Using diodes, alternating voltages can be rectified. 

Obtain an expression for the electric field \( \vec{E} \) due to a dipole of dipole moment \( \vec{p} \) at a point on its equatorial plane and specify its direction.
Hence, find the value of electric field:

1. at the centre of the dipole (\( r = 0 \))
2. at a point \( r \gg a \), where \( 2a \) is the length of the dipole.