Question Discussion & Solution

The diagram that best represents the relationship among Sun, Moon and Universe:

Both the Sun and Moon belong to the universe.

Hence, ‘option 2’ is the correct answer.

Ammeter is an instrument used to measure Current.

Similarly, Hygrometer is an instrument used to measure Humidity

The correct answer is Its momentum is doubled.

Key Points

• Momentum is a vector quantity; it has both magnitude and direction.
• Isaac Newton’s second law of motion states that the time rate of change of momentum is equal to the force acting on the particle.
• Momentum can be calculated by multiplying the mass of an object by its forward velocity. (mv = kg*m/s).
• Mass and velocity are both directly proportional to the Momentum.
  • If you increase either mass or velocity, the Momentum of the object increases proportionally.
  • If you double the mass or velocity, you double the Momentum.
  • If you halve the mass or velocity, you half the Momentum.
• Newton's laws of motion-
  • ​Newton’s first law states that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by force. This postulate is known as the law of inertia.
  • Newton’s second law is a quantitative description of the changes that a force can produce in a body's motion. It states that the time rate of change of a body's momentum is equal in both magnitude and direction to the force imposed on it. The momentum of a body is equal to the product of its mass and its velocity.
  • Newton’s third law states that when two bodies interact, they apply forces to one another equal in magnitude and opposite in direction. The third law is also known as the law of action and reaction. This law is important in analyzing static equilibrium problems, where all forces are balanced, but it also applies to bodies in uniform or accelerated motion.

Important Points

• Acceleration, the rate at which velocity changes with time in terms of both speed and direction. A point or an object moving in a straight line is accelerated if it speeds up or slows down. Motion on a circle is accelerated even if the speed is constant because the direction is continually changing.
• Kinetic energy, a form of energy that an object or a particle has because of its motion. If work, which transfers energy, is done on an object by applying a net force, the object speeds up and gains kinetic energy. Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass.
• Potential energy, stored energy that depends upon the relative position of various parts of a system. Spring has more potential energy when it is compressed than stretched. A steel ball has more potential energy raised above the ground than it has after falling to Earth.

Given,

Given Expression: 70S7P21R2Q15

According to question :

=70 ÷ 7 + 21 × 2 – 15

Using BODMAS rule,

=10 + 21 × 2 – 15

= 10 + 42 – 15

= 52 – 15

= 37

Hence, value of the given expression is ‘37’.

The correct answer is Nichrome.

Key Points

• Nichrome 
  • It is a metal alloy made up of around 20 percent of chromium and 80 percent nickel.
  • The key to the workings of an electrical heating element is the role of the nichrome in it.
  • Nichrome has fast emerged as the leading alloy to be used in terms of electrical heating elements.
  • For an electric iron heater element should have higher resistance, high melting point, and high specific heat.
  • An element should have high resistance so that it can hold its configuration in a high voltage current. It should have a high melting point such that it can sustain high temperatures.
  • Nichrome is used as a heating element in electric iron which is an alloy consisting 80% of Nickel and 20% of Chromium melting point of this element is 1400 degrees Celsius with high resistance which makes this element best for use as a heating element. Hence, Option 1 is correct.
  • The reason which makes the Nichrome best for heating elements is when it is heated in the air it develops an outer layer of chromium oxide which makes it stable in air and this chromium layer helps the element from oxidizing further during heating. 

Additional Information

• Copper
  • It is a chemical element with the symbol Cu and atomic number 29.
  • It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity.
  • A freshly exposed surface of pure copper has a pinkish-orange color.
• Silver
  • It is a chemical element with the symbol Ag and atomic number 47.
  • A soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal.
• Lead
  • It is a chemical element with the symbol Pb and atomic number 82.
  • It is a heavy metal that is denser than most common materials.
  • Lead is soft and malleable, and also has a relatively low melting point.
  • When freshly cut, lead is silvery with a hint of blue it tarnishes to a dull gray color when exposed to air.