A photoelectric device in which the resistance of the metal changes directly proportional to the light striking on it is called
photoconductive cell
Understanding Photoelectric Devices and Resistance Changes
The question asks to identify a specific type of photoelectric device. The key characteristic described is that the device's resistance of the metal changes in direct proportion to the amount of light striking it.
Analyzing the Options
Let's examine each option to see which one fits the description:
- Photocell: This is a general term for any electronic device that exhibits photoconductivity or photoelectric properties. While a photoconductive cell is a type of photocell, the term itself isn't specific enough to describe the unique property mentioned.
- Photoemission Cell: This device works on the principle of photoemission, where light striking a material causes it to emit electrons. Its primary function is not related to a change in resistance proportional to light intensity.
- Photovoltaic Cell: This cell converts light energy directly into electrical energy (voltage and current) via the photovoltaic effect. It generates power, but the defining characteristic isn't a change in resistance proportional to light.
- Photoconductive Cell: This device is specifically designed so that its electrical resistance decreases as the intensity of incident light increases. This decrease in resistance is often approximately proportional to the light intensity, matching the question's description perfectly. These are also commonly known as photoresistors.
Conclusion on Device Property
The core principle highlighted in the question is the change in electrical resistance directly linked to the intensity of incoming light. This behavior is the defining characteristic of a photoconductive cell. When light falls on the semiconductor material within a photoconductive cell, more charge carriers are generated, increasing conductivity and thus decreasing resistance.
In simpler terms, more light means less resistance, and this relationship is what makes a photoconductive cell the correct answer.
Therefore, the photoelectric device where the resistance of the metal changes directly proportional to the light striking on it is called a photoconductive cell.
Important Questions from Miscellaneous
A stone is thrown horizontally from the top of a 20 m high building with a speed of 12 m/s. It hits the ground at a distance R from the building. Taking g = 10 m/s2 and neglecting air resistance will give :
A sphere of volume V is made of a material with lower density than water. While on Earth, it floats on water with its volume f1V (f1 < 1) submerged. On the other hand, on a spaceship accelerating with acceleration a < g (g is the acceleration due to gravity on Earth) in outer space, its submerged volume in water is f2V. Then:
A railway wagon (open at the top) of mass M1 is moving with speed v1 along a straight track. As a result of rain, after some time it gets partially filled with water so that the mass of the wagon becomes M2 and speed becomes v2. Taking the rain to be falling vertically and the water stationery inside the wagon, the relation between the two speeds v1 and v2 is :
Consider the following statements:
1. Distance between the longitudes becomes zero on North Pole and South Pole.
2. Distance between the longitudes is maximum on the Equator.
3. Number of longitudes is more than number of latitudes.
Which of the statements given above is/are correct?
One block of 2⋅0 kg mass is placed on top of another block of 3⋅0 kg mass. The coefficient of static friction between the two blocks is 0⋅2. The bottom block is pulled with a horizontal force F such that both the blocks move together without slipping. Taking acceleration due to gravity as 10 m/s2, the maximum value of the frictional force is :
