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Define resistivity.
Out of the following bulbs rated 40 W, 220 V, 60 W, 220 V and 100 W, 220 V, which one will glow the brightest when connected in series to a supply of 220 V?
State the factors that alter the resistance of a conductor. Write the mathematical expression.
State Joules low of heating and give its expression.
Why the cord of a heating element does not glow while the heating element glows?
What is the commercial unit of electrical energy? Convert it into joule. What is the other name of the commercial unit? What is meant by a parallel combination of resistors? Deduce an expression for the equivalent resistance when two resistor are connected in parallel.
Two resistors of 5 Ω and 10 Ω are connected in parallel. Eight such sets are connected in series.
Find the equivalent resistance of this combination.
In the circuit shown in figure, calculate
(i) the current through the arms AB, AC and CDE,
(ii) the potential difference across AB, CD and DE.
Find the equivalent resistance of the following combination of resistors:
(a) Express ohm’s law by a mathematical formula.
(b) Draw a circuit diagram to verify ohm’s law.
(c) Present the relationship between the voltage applied across a conductor and the current flowing through it graphically.
No current flows between two charged bodies when connected, if they have the same:
If a wire of resistance R is melted and recast to half of its length, then new resistance of the wire will be:
n equal resistors are first connected in series and then connected in parallel. The ratio of the maximum to the minimum resistance is:
If R1 and R2 are the resistances of filaments of a 400 W and a 200 W lamp, designed to operate on the same voltage, then:
In a circuit containing two unequal resistors connected in parallel:
The equivalent resistance in series combination is:
A house is fitted with 5 tubes each f 40 W. If all the tubes are lighted for 20 hours and if the cost of electrical unit is Rs. 0.50, the total cost of electricity consumed is:
Of the two bulbs in a house, one glows brighter than the other. Which of the two has a larger resistance?
You are given a resistance wire of length 50 cm and a battery of negligible resistance. In which of the following cases is the largest amount of heat generated:
You are given three bulbs of 25 W, 40 W and 60 W marked at 220 V. Which one of them has lowest resistance?
The potential difference across a conductor is doubled, the rate of generation of heat will:
What are the essential requirements of a heater filament?
Two wires of the same metal have the same length, but cross-sections are in the ratio 3:1. They are joined in series. The resistance of the thicker wire is 10 Ω. The total resistance of the combination will be:
You are given three equal resistors. The number of resistances which can be obtained by joining them is series and in parallel grouping is:
Write true or false for the following statements:
The unit of measurement of charge is coulomb.
A metal has a very large number of free electrons and a non-metal very less number of free electrons.
An electron in a metal is free to move anywhere but cannot leave the metal.
Potential and potential difference are vector quantities.
Potential is positive of positively charged body and is negative of a negatively charged body.
Positive charges flow from high potential to low potential.
Battery is a source of maintaining a constant potential difference across two ends of a conductor.
The units of resistance are ampere.
If the resistance of a conductor is doubled, the current is halved.
Resistance of a conductor increases with the increase in temperature.
Insulator like wood and rubber has a very low electrical resistance.
If resistors are connected in series, the current through each resistor remains the same.
If resistors are connected in parallel, the voltage across each remains the same.
Resistance of a piece of rubber is more than that of a piece of copper.
Electric power of a circuit is the rate at which work is done in maintaining the electric current in the circuit.
1 kWh = 3.6 × 106 joule
Electric power is also called BOTU.
Heat dissipated by a conductor when a current is passed through it is directly proportional to the resistance of the conductor.
Electric bulb works on heating effect of current.
The electrical appliance having higher power draws a larger current.
The quantity of charge flowing past a point multiplied by time is current.
The flow of charge through a conducting wire connected to a cell is the result of chemical reaction inside the cell.
The resistivity of all pure metals increases with increase in temperature.
Ohm’s law is a relation between the power used in a circuit to the current and the potential difference.
A series circuit has only one conducting path for the electrons that move through it; a parallel circuit has multiple conducting paths.
A conducting wire offers resistance to the flow of electrons because electrons repel each other in the wire.
