Test: Electricity & Magnetism - Software Development MCQ

Concept:

• Electric current is the rate of flow electric charge or free Electrons in a definite direction through any section of wire. Its SI unit is ampere(A).
• The direction of the conventional current corresponds to the direction of positive charge which is from higher potential(positive) to lower potential(negative).

I = Q / t

I is current, Q is charge, t is time

Explanation:

Q = I t

So Charge is the product of current and time.

Unit of current is Ampere, and unit of time is an hour. 

So, Amount of charge or Quantity of electricity is Ampere-hour 

The correct answer is Ammeter. 

Key Points

• An ammeter is the instrument used to measures the electric current in a circuit.
• Electricity is the flow of free electrons.
• Unit of Current - Ampere.
• Father of  Electricity - Michael Faraday. 

Additional Information

Ohmmeter

• The instrument used to measure the electrical resistance.
• Electrical resistance opposes the flow of electric current in a circuit.
• Unit of Resistance - Ohm
• Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points.
• V=IR, where (R) Resistance is the proportionality constant.

Thermometer

• An instrument used to measure the temperature.
• The first Mercury Thermometer was invented by Gabriel Fahrenheit.

​Gyroscope

• The instrument used to measure or maintaining the orientation of angular velocity.
• Gyroscope was invented by Leon Foucault.

The correct answer is option 4) i.e. All of the above

Concept:

• Magnetic field: The region around a magnet where its influence is experienced is called the magnetic field.
  • The visual representation of the magnetic field is called magnetic field lines.

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• ​Properties of magnetic field lines:
  1. ​​The field lines start from the north pole and end at the south pole.
  2. The field lines are crowded where the magnetic field is the strongest.
  3. The field lines form continuous curves.
  4. The field lines do not intersect.

Explanation:

• The magnetic field is strongest near the poles. Since magnetic field lines start and end at poles, they converge towards the region of strong magnetic force.
• Two magnetic field lines cannot intersect. If they did, at the point of intersection, the magnetic field will have two directions - which is not possible.
• The magnetic field lines have direction as they are represented as flowing, though no actual movement occurs. So, they do not move.

Therefore, all the given statements are true.

Concept:

• Electroscope:
  • It is an early scientific instrument used to detect the presence of an electric charge on a body.
  • The first electroscope was a pivoted needle electroscope invented in the year 1600 by British Physicist William Gilbert.
  • It measures the charge that is dependent on the Coulomb electrostatic force that triggers the movement of the test charge.

Explanation:

• Seismograph:
  • It is an instrument that is used to detect and record earthquakes. generally, it consists of a mass attached to a fixed base. During an earthquake, the base moves and the mass does not.
• Ammeter:
  • This is a meter that is used for measuring electric current. Current is the flow of electrons whose unit is ampere.
  • Hence the instrument which measures the flow of current in ampere is called as Ampere meter or ammeter.
  • the ideal ammeter has zero internal resistance.
• Voltmeter:
  • It is an instrument used for measuring the electric potential difference between two points in an electric circuit that is connected in parallel. 
  • It usually has high resistance so that it takes negligible current from the circuit.
•  An electroscope is a correct answer.

The correct answer is Lactometer.

• Some other important measuring instruments are:

The correct answer is Hygrometer.

Key Points

• Hygrometer
  • A hygrometer is an instrument for measuring the relative humidity of the atmosphere.
  • The hygrometer was invented by Leonardo da Vinci.

Additional Information

• ​Barometer
  • A barometer is an instrument used to measure atmospheric pressure.
  • The barometer was invented by Torricelli.
• Hydrometer
  • A hydrometer is an instrument used to measure the specific gravity of liquids.
  • The hydrometer was invented by Nicholson.
• ​Anemometer
  • An anemometer is an instrument used to measure the velocity of wind and directions.
  • The anemometer was invented by Leon Alberti.

Concept:

• The pressure cooker is based on the principle that the boiling of water increases with the increase in pressure.

Explanation:

• When we give heat to the pressure cooker then due to an increase in temperature the steam generated in the vessel.
• Due to this generated steam, the pressure inside the vessel increases. So the food gets cooked soon.
• Thus by the application of pressure the boiling point of the water increases. Hence option 1 is correct.
• There is no relation between food-grains with the boiling point of water. So options 2, 3, and 4 are wrong.

Concept:

• The battery has two terminals positive and negative its positive terminal is the anode and its negative terminal is the cathode.
  • It works on the principle of Electrochemical Reaction.
  • Italian physicist Alessandro Volta built and described the first electrochemical battery, the voltaic pile, in the year 1800.
  • The lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics such as laptops and mobile phones.

Explanation:

• A battery converts chemical energy into electrical energy. So option 3 is correct.

Concept:

• Any battery (actually it may have one or more than one cell connected in series) or cell that we use as a source of electrical energy is a galvanic cell where the chemical energy of the redox reaction is converted into electrical energy. 
• In the primary batteries, the reaction occurs only once, and after use over some time battery becomes dead and cannot be reused again.
• The most familiar example of this type is the dry cell (known as Leclanche cell after its discoverer) which is used commonly in our transistors and clocks. 
• The cell consists of a zinc container that also acts as cathode and the anode is a carbon (graphite) rod surrounded by powdered manganese dioxide and carbon.
• The space between the electrodes is filled by a moist paste of ammonium chloride (NH₄Cl) and zinc chloride (ZnCl₂). 

Explanation:

• The cell consists of a zinc container that acts as the Cathode.
• The anode is a carbon (graphite) rod surrounded by a cathodic material powder of manganese dioxide and carbon.

So, The positive pole of the dry cell is made up of C (carbon).

Concept:

• Newton's first law states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by any external force.
• Newton's Second Law of motion states that the rate of change of momentum of an object is proportional to the applied force in the direction of the force i.e.,

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Where F = force applied, m = mass of the body, and a = acceleration produced.

• Newton's Third Law of Motion states that 'To every action, there is an equal and opposite reaction'.

Explanation:

• The launching of a rocket illustrates Newton’s third law of motion. Therefore the option 1 is correct.
• Newton's Third Law of Motion states that 'To every action, there is an equal and opposite reaction'.
• So, when the rocket is ignited, it releases gases from its thrusters thereby creating a force that will push rocket upwards and it can gain extreme velocity using this principle.

Important Point

• Newton's third law of motion is applicable irrespective of the nature of the forces. The forces of action and reactions may be mechanical, gravitational, electric, or of any other nature.
• Action and reaction always act on different bodies. If they acted on the same body, the resultant force would be zero and there could never be accelerated motion.
• The forces of action and reaction cannot cancel each other. This is because action and reaction, though equal and opposite, always act on different bodies and so cannot balance each other.
• No action can occur in the absence of a reaction.