Explanation

The head-to-tail rule is a method for adding vectors, such as forces, by lining up the head of one vector with the tail of the next vector.

This rule can be used to add any number of forces, not just two or three.

Explanation

The transistor is a semiconductor device with at least three terminals.

These terminals are typically referred to as the :

• Emitter
• Base
• Collector

They allow the transistor to control the flow of electrical signals and power. 

Explanation

Total distance = Length of train + Length of bridge = 100 m + 200 m = 300 m  

Speed = 15 m/s  

Time = Distance / Speed = 300 / 15 = 20 seconds

Explanation

A body moving in a circular path with constant speed has variable acceleration. 

While the speed remains constant, the direction of the velocity vector is constantly changing as the body moves around the circle.

Since acceleration is the rate of change of velocity, and velocity is changing (even though speed is constant),

The body experiences a constant magnitude of acceleration

But the direction of that acceleration changes at every point on the circle.

This makes the acceleration variable. 

Explanation

 A device based on the photoelectric effect is called a photodiode. 

 A photodiode is a semiconductor device that converts light into electrical current by absorbing photons and generating electron-hole pairs, essentially utilizing the photoelectric effect. 

Explanation

Given:

• Radius of the circle$r=4$ meters

• Arc length (distance along the circumference), $s=14$ meters

We are to find the displacement, which is the straight-line distance between the starting and ending points of the arc.

Step 1: Find the angle subtended by the arc at the center (θ in radians):

$$theta = frac{s}{r} = frac{14}{4} = 3.5 , text{radians}$$

Step 2: Use the chord length formula to find displacement:

Displacement=2rsin(θ/2​)
=2×4×sin(3.5/2​)=8×sin(1.75)
sin(1.75radians)≈0.983
$$\text{Displacement}\approx 8\times 0.983\approx 7.864\text{meters}$$

Explanation

A heat detector is used for finding fires by detecting significant increases in temperature

Types:

Some heat detectors respond to a rapid temperature increase ("rate-of-rise"),

While others activate when a specific temperature is reached ("fixed temperature"). 

Explanation

Electronics comprises the:

• Physics: Study of electrons, semiconductors, and electronic behavior.
• Engineering: Design, development, and testing of electronic systems and devices.
• Technology: Application of electronic principles to create devices, circuits, and systems.

Explanation

The human eye acts like a Camera, capturing light and focusing it onto the retina to form an image.

The eye's lens, aperture, and retina work together to create a visual representation of the world, similar to a camera's mechanism.

Explanation

A solid has a fixed shape and a definite volume, regardless of its container.

The particles (molecules, atoms, or ions) in a solid are closely packed and have a fixed position, giving the solid its rigidity and shape.