Free NCERT Solutions For Class 10 Science Chapter 12 Electricity download in PDF form. All chapters of Class 10 Science are available in PDF form. Study online or download to use it offline.
NCERT Solutions For Class 10 Science Chapter 12
Class 10 Physics – Electricity
Extra Questions with Answers – for board exams preparation
What is an electric circuit? Distinguish between an open and a closed circuit.
A closed and continuous path along which an electric current flows is called an electric circuit.
In a torch, a switch provides a conducting link between a battery (a number of cells placed in proper order) and a bulb. When the switch is turned ON, an electric current flow through the bulb and its gives light. Such a continuous and closed path on an electric current is called an electric circuit. When the circuit is broken anywhere (or switch is turned OFF), the current stops flowing ant the bulb does not glow. An electric circuit through which no current flows is called an open circuit. An electric circuit through which current flows continuously is called a closed circuit.
Distinguish between conventional current and electronic current. Or In an electric circuit state the relationship between the direction of conventional current and the direction of flow of electrons.
conventional current and electronic current: When a conductor AB is connected across the terminals of a cell , free electrons begin to drift or move from its end B (connected to the negative terminal of the cell) to the end A (connected to the positive terminal of the cell). The current constituted by flowing electrons is called electronic current. Clearly, the direction of electronic current is from negative terminal to positive terminal.
By convention, the direction of motion of positive charges is taken as the direction of electric current. It is from positive terminal to negative terminal. As the electrons are negatively charged, the direction of conventional current is an electric circuit is taken as opposite to the direction of the flow of electrons.
What is an ammeter? How is it connected in a circuit?
Ammeter: An ammeter (ampere + meter) is a device used to measure electric current in a circuit. An ammeter is always connected in series in a circuit, so that entire current, which we wish to measure, flows through it.
What is meant by potential difference between two points? What is the SI unit of potential difference?
Potential difference: The potential difference between two points in an electric field is the amount of work done in bringing a unit positive charge from one point to the other.
V = W/Q or Potential difference = Work done / Charge
The SI unit of potential difference is joule/coulomb or volt.
List two differences between a voltmeter and an ammeter.
(i) It measures potential difference between two points in a circuit.
(ii) It is connected in parallel with the component across which p.d. is measured
(i) It measures current passing through a circuit.
(ii) It is connected in series in a circuit.
State Ohm’s law and write the condition in which this law is obeyed?
This law states that the current (I) flowing through a conductor is directly proportional to the potential difference (V) applied across its ends, provided the temperature and other physical condition remain unchanged.
Mathematically, V ∝ I or V = RI
The proportionality constant R is called the resistance of the conductor.
What is meant by resistance of a conductor?
Resistance: The resistance of a conductor is its property by virtue of which it opposes the flow of current through it. It is equal to the ratio of the potential difference applied across the conductor to the current flowing through it.
Resistance = Potential difference / Current Or R = V/I.
What is the function of rheostat in an electric circuit.?
It changes the current in a circuit due to the change in its resistance.
List the factors on which the resistance of a conductor depends. Write the formula showing relation of resistance with these factors.
Factors affecting the resistance: At a constant temperature, the resistance of a conductor depends on the following factors:
(i) Length: Resistance R of a conductor is directly proportional to its length L, i.e.,
R ∝ L
(ii) Area of cross-section: Resistance R of conductor is inversely proportional to its area of cross-section A, i.e.,
R ∝ 1/A
(iii) Nature of the material: Resistance also depends on the nature of the material of which the conductor is made. The resistance of copper wire is much less than that of a nichrome wire of same length and area of cross-section.
Combining the above factors, we get,
R ∝ L/A ⇒ R = ρ L/A
The proportionality constant ρ is called resistivity or specific resistance which depends on the nature of the material.
Give four reasons why nichrome element is commonly used in household appliances.
In most of the household heating appliance, nichrome element is used because of the following reasons:
(i) Its melting point is high.
(ii) Its resistivity is large.
(iii) It can be easily drawn into thin wire.
(iv) It is not easily oxidised by the oxygen of the air when heated.
Why does the cord of an electric heater not glow while the heating element does?
Both the cord and the heating element of an electric heater carry the same current. But the heating element becomes hot due to its high resistance (H=I²Rt) and begins to glow. The cord remains cold due to its low resistance and dos not glow.