Home
Class 12
BIOLOGY
A - Nerve fibre can become excited throu...

A - Nerve fibre can become excited through touch, smell, pressure and chemical changes and there is a change in polarity.
R- It is called active potential.

A

A and R both are correct but A is not correct explanation of R.

B

A and R both are correct and A is correct explanation of R.

C

A is correct and R is wrong

D

A is wrong and R is correct

Text Solution

Verified by Experts

Promotional Banner

Similar Questions

Explore conceptually related problems

The helicopter has a mass m and maintains its height by imparting a downward momentum to a column of air defined by the slipstream boundary as shown in figure. The propeller blades can project a downward air speed v_0 , where the pressure in the stream below the blades is atmospheric and the radius of the circular cross section of the slipstream is r . Neglect any rotational energy of the air, the temperature rise due to air friction and any change in air density rho . If the power is doubled, the acceleration of the helicopter is :-

The helicopter has a mass m and maintains its height by imparting a downward momentum to a column of air defined by the slipstream boundary as shown in figure. The propeller blades can project a downward air speed v, where the pressure in the stram below the blades is atmospheric and the radius of the circular cross section of the slipstream is r. Neglect any rotational energy of the air, the temperature rise due to air friction and any change in air density rho . If the power is doubled, the acceleration of the helicopter is :-

Each phase of a material can exits only in certain regions of pressure and temperature . P-T phase diagrams, in which pressure is plotted versus temperature, show the regions corresponding to various phases and phase transformations . P-V diagrams, on the other hand , can be used to study pressure volume relationship at a constant temperature. If the liquid and gaseous phases of a pure substances are heated together in a closed container, both the temperature and the vapor pressure will increase until a point is reached at which the two phases can no longer be distinguished from one another. The temperature and pressure at which this occurs are called the critical temperature and pressure. Exceeding either of these parameters, by itself ,will cause the "gas"//"liguid" phase transition to disappear. if the other variable is then changed as well, while the first variable is maintained above its critical point , a gradual transition will occur between the gaseous and liquid phases, with no clear boundary.(The liquid and solid phases, on the other hand , maintain a distinct boundary at all pressure above the triple point). Shown in figure is a combined P-T phase diagram for material A and B . If heat is added to solids A and B , each in a container that is open to the atmosphere :-

Each phase of a material can exits only in certain regions of pressure and temperature . P-T phase diagrams, in which pressure is plotted versus temperature, show the regions corresponding to various phases and phase transformations . P-V diagrams, on the other hand , can be used to study pressure volume relationship at a constant temperature. If the liquid and gaseous phases of a pure substances are heated together in a closed container, both the temperature and the vapor pressure will increase until a point is reached at which the two phases can no longer be distinguished from one another. The temperature and pressure at which this occurs are called the critical temperature and pressure. Exceeding either of these parameters, by itself ,will cause the "gas"//"liguid" phase transition to disappear. if the other variable is then changed as well, while the first variable is maintained above its critical point , a gradual transition will occur between the gaseous and liquid phases, with no clear boundary.(The liquid and solid phases, on the other hand , maintain a distinct boundary at all pressure above the triple point). Shown in figure is a combined P-T phase diagram for material A and B . Which is true about the substance in figure?

In a p-n junction diode, the current I can be expressed as I=I_(0)"exp"((eV)/(2k_(B)T)-1) where I_(0) is called the reverse saturation current, V is the voltage across the diode and is positive for forward bias and negative for reverse bias, and I is the current through the diode, k_(B) is the Boltzmann constant (8.6xx10^(-5)eV//K) and T is the absolute temperature. If for a given diode I_(0)=5xx10^(-12) A and T = 300 K, then (a) What will be the forward current at a forward voltage of 0.6 V ? (b) What will be the increase in the current if the voltage across the diode is increased to 0.7 V ? (c ) What is the dynamic resistance? (d) What will be the current if reverse bias voltage changes from 1 V to 2 V ?

In a p-n junction diode, the current I can be expressed as I= I_(0) "exp" ((eV)/(2k_(B)T)-1) where I_(0) is called the reverse saturation current, V is the voltage across the diode and is positive for forward bias and negative for reverse bias, and I is the current through the diode, k_(B) is the Boltzmann constant (8.6 xx 10^(–5) eV//K) and T is the absolute temperature. If for a given diode I_(0) = 5 xx 10^(-12) A and T = 300 K, then (a) What will be the forward current at a forward voltage of 0.6 V? (b) What will be the increase in the current if the voltage across the diode is increased to 0.7 V? (c) What is the dynamic resistance? (d) What will be the current if reverse bias voltage changes from 1 V to 2 V?

An insulated cylinder is divided into three parts A, B and C. Pistons 1 and 2 are connected by a rigid rod and can slide without friction inside the cylinder. Piston 1 is perfectly conducting while piston 2 is perfectly insulating. Equal quantity of an ideal gas is filled in three compartments and the state of gas in every part is same (P_(0) V_(0) T_(0)) . Adiabatic exponent of the gas is g = 1.5. The compartment B is slowly given heat through a heater H such that the final volume of gas in part C becomes (4V_(0))/(9) (a) Calculate the heat supplied by the heater. (b) Calculate the amount of heat flow through piston 1. (c) If heater were in compartment A, instead of B how would your answers to (a) and (b) change?

In the shown expermiental setup to study photoelectric effect, two conducting electrodes are enclosed in an evacuated glass-tube as shown. A parallel beam of monochromatic light, falls on photosensitive electrodes. The emf of battery shwon is high enough such that all photoelectron ejected from left electrode will reach the right electrode. Under initial conditions photoelectrons are emitted. AS changes are made in each situation of column-I, Match the statements in column-I with results in column-II. {:(,"Column I",,"Column II"),((A),"If frequency of incident light is increased keeping its intensity constant",(p),"magnitude of stopping potential"),((B),"If frequency of incident light is increased and its intensity is decreased",(q),"current through circuit may stop"),((C),"If work function of photo sensitive electrode is increased",(r),"maximum kinetic energy of ejected photoelectrons will increase"),((D),"If intensity of incident light is increased keeping its frequency constant",(s),"saturation current will increase"):}

An electromagnetic wave can be represented by E = A sin (kx- omega t + phi) , where E is electric field associated with wave, According this equation, for any value of x, E remains sinusoidal for -oolt t lt oo . Obviously this corresponds to an idealised situation because radiation from ordinary sources consists of finite size wavetrains. In general, electric field remains sinusoidal only for times of order tau_(c) ' which is called coherence time. In simpler language it means that for times of order tau_(c)' a wave will have a definite phase. The finite value of coherence time could be due to many factors, for example if radiating atom undergoes collision with another atom then wave train undergoes an abrupt phase change or due to the fact that an atom responsible for emitting radiation has a finite life time in the energy level from which it drops to lower energy level, while radiating. Concept of coherence time can be easily understood using young's double slit experiment. Let interference patten is observed around point P at time t , due to superposition of waves emanting from S_(1) and S_(2) at times t =(r_(1))/(c) and (r_(2))/(c) respectively, where r_(1) and r_(2) are the distances S_(1) P & S_(2)P . Obviously if (r_(2)-r_(1))/(c) lt lt tau_(e),{"where" " "c = 3xx10^(8)m//s} then, wavetrain arriving at point P from S_(1) & S_(2) will have a definite phase relationship and an interference pattern of good contranst will be obtained. If coherence time is of order 10^(-10) second and screen is placed at a very large distance from slits in the given figure, then:-