Explore topic-wise InterviewSolutions in .

A .  copper.

B. resistors

Resistance is a measure of a material’s opposition to current.

D. All the above

C. electric charge in units of coulomb per s.

B. wiper and resistor track

A freshly prepared cell has Low internal resistance.

Correct answer is (b) 0.5 Ω

In the electrolyte of the cell, current flows from Negative to positive terminal.

Mercury becomes a superconductor at 4.2 K.

The SI unit of power is Watt

A continuous flow of electrons constitutes an electric current in a metal.

The SI unit of electric current is the ampere.

The SI unit of electric potential is the volt.

(i) Buoyant force. It is a vector quantity. Others are scalar quantities.

(ii) Electric bell. Its working is based on the magnetic effect of electric current. The working of other devices is based on the heating effect of electric current.

The graphite rod at the centre is the positive terminal of the dry cell.

The electric current in an external circuit flows from the Positive to negative terminal.

A liquid flows from a higher level to a lower level. Heat flows from a body at a higher temperature to a body at a lower temperature. Also when different parts of a body are at different temperatures, heat flows from the part at a higher temperature to the part at a lower temperature.

Similarly, a positive charge (free to move) flows from a point at a higher electric level to a point at a lower electric level and a negative charge (free to move) flows from a point at a lower electric level to a point at a higher electric level. The electric level deciding the direction of flow of electric charge is called electrostatic potential (electric potential).

The temperature coefficient for alloys is Low.

Correct answer is (а) 1 A

The reciprocal of resistance is Conductance.

Charging is a process of reproducing Active materials.

With increase in temperature the resistivity of metals Increases.

A continuous path consisting of conducting wires, a switch or a plug key and other resistances (for example, resistance of an electric bulb) between the terminals of a cell (or a battery) along which an electric current flows is called an electric circuit.

The inverse of the effective resistance is equal to the sum of the inverses of individual resistances. The current flowing through an individual resistor is proportional to the r inverse of its resistance and the total current flowing through the circuit is the sum of the currents flowing through individual resistors. The potential difference across all r resistors is the same. The effective resistance of resistors connected in parallel is less than r the least resistance of individual resistors.

This arrangement is used to reduce the resistance in a circuit. Even if any one of the several bulbs connected in parallel becomes non-functional because of some damage to its filament, the circuit does not break as the current flows, through the other paths, and the rest of the bulbs light up. When several bulbs are connected in parallel, they emit the same amount of light as when they are connected individually in the circuit, while bulbs connected in series emit less light than when connected individually.

(i) Electric switches and sockets should be fitted at a height at which small children cannot reach and put pins or nails inside.

(ii) Plug wires should not be pulled out while removing any electrical device as it may cause the wire to break causing short circuit which can lead to fire or death.

(iii) As rubber is an insulator, it prevents the current from flowing through our body, thereby protecting it. Hence a person should wear footwear with rubber soles while handling electrical appliances.

(iv) We will advise her to dry her hands before touching any electrical sockets or devices as water on the hands can cause an electrical short circuit producing shock to the person touching it.

(v) We should switch off the main switch and if the switch is too far or we do not know where it is located, then we should remove the plug from the socket if possible. If not, then we should use a wooden pole to push the person away from the electric wire.

(vi) Precautions to be taken while using electricity

Except current the values of all the other quantities depends upon the area of cross section of the conductor. Hence, only current remains constant, when it flows through a conductor of non-uniform area of cross-­section.

The cells are connected (1) in series to get maximum voltage, (2) in parallel to get maximum current. 

(a) 0.5 Ω

r =\(\frac{ξ}{I}\)= \(\frac{1.5}{3}\) = 0.5 Ω.

Superconductor

Nichrome is an ohmic resistance.

Hint: Substances that obey Ohm's law are called Ohmic resistors.

A small wire present inside the bulb is called as Filament.

The value of shunt resistance required to convert a galvanometer into an ammeter is given by,

S = \(\left(\cfrac{I_g}{I-I_g}\right)G\)

If the current I is p times the current I_g , then I = pI_g . Using this in the above expression, we get,

S = \(\cfrac{GI_g}{pI_g-I_g}\) OR

S = \(\cfrac{G}{p-1}\)

This is the required shunt resistance to increase the range p times.

A. volts = current times resistance

The resistance of the wire varies inversely as Area of cross section.

Voltage is a form of Potential energy.

The curve representing Ohms law is a  Linear.

The ratio of voltage and electrical current in a closed circuit Remains constant.

Electric current originates from negatively charged electrons.

(B) Electrical forces are produced by electrical charges.

Electrons have been removed produce positive electric charge & a negative charge

A. Friction between the comb and hair transfers electrons.

Infinity 

The resistance of a voltmeter should be very high and for an ideal voltmeter, its value is infinity.

The potential difference between two points is said to be 1 volt if 1 joule of work is done in moving 1 coulomb of electric charge from one point to another.

1 V = \(\cfrac{1\,J}{1\,C}\)

If the physical state of a conductor remains constant, the current (I) flowing through it is directly proportional to the potential difference (V) between its two ends.

V = IR

The amount of work done to carry a unit positive charge from point A to point B is called the electric potential difference between the two points.

V = \(\cfrac{W}{Q}\)

Those substances which have very low resistance are called conductors. Current can flow easily through such materials.

• Those substances which have infinitely high electrical resistance are called insulators. 
• Wood and glass have high resistance and negligible free electrons for conduction of electricity. 
• Hence, wood and glass are good insulators.

• The resistance (R) of a wire is inversely proportional to the cross-sectional area (A) of a wire. i.e., R i
• Thus, greater is the cross-sectional area of a conductor (wire), lower is its resistance. Hence, a thick wire has a low resistance.

Those substances which have extremely high resistance and through which current cannot flow are called insulators.