# CURRENT ELECTRICITY

Detailed Study:

Brief Revision - Important Question Solving:

https://www.youtube.com/watch?v=DfBOFVD0SJ0&list=PLhf4hr_x5XyTwhfUuatWM0RJ8BfdPyb7L&index=16

## LIST OF FACTORS AFFECTING RESISTANCE, RESISTIVITY, INTERNAL RESISTANCE, HEATING EFFECT, ETC.

## IMPORTANT FORMULAE FOR ELECTRICITY NUMERICALS

## Important Past Questions:

##

## You have three resistors of values 2Ω, 3Ω and 5Ω, how will you join them so that the total resistance is more than 7 Ω?

## i) Draw a diagram for the arrangement.

## ii) Calculate the equivalent resistance.

## (2018)

## Define specific resistance and state its S.I unit.

## (2017)

## An electric bulb of resistance 500 Ω draws a current of 0.4 A. Calculate the power of the bulb and the potential difference at its end.

## (2017)

## A music system draws a current of 400mA when connected to a 12V battery.

## i) What is the resistance of the music system?

## ii) The music system is left playing for several hours and finally the battery voltage drops and the music system stops playing when the current drops to 320 mA. At what battery voltage does the music system stop playing.

## (2016)

## What happens to the resistivity of semiconductors with the increase of temperature?

## (2015)

## What is consumed using different electrical appliances, for which electricity bills are paid?

## (2014)

## An electrical appliance is rated at 1000 kVA, 220V. If the appliance is operated for 2 hours, calculate the energy consumed by the appliance in:

## i) kWh

## ii) joule

## (2012)

## Two bulbs are marked 100W, 220V and 60W, 110V. Calculate the ratio of their resistances.

## (2011)

## Write an expression for calculating electrical power in terms of current and resistance.

## (2011)

## State a relation between electrical power, resistance and potential difference in an electrical circuit.

## (2010)

## An electric heater is rated 1000W-200V. Calculate:

## i) the resistance of the heating element

## ii) the current flowing through it

## (2009)

## Sketch a graph to show the change in potential difference across the ends of an ohmic resistor and the current flowing in it. Label the axis of your graph. What does the slope of the graph represent?

## (2008, 2011, 2015)

## An electrical heater is rated 4kW, 220V. Find the cost of using this heater for 12 hours if one kWh of electrical energy costs ₹3.25.

## (2008)

## Calculate the value of the resistance which must be connected to a 15 Ω resistance to provide an effective resistance of 6Ω.

## (2007)

## A wire of uniform thickness with a resistance of 27 Ω is cut into three equal pieces and they are joined in parallel. Find the resistance of the parallel combination.

## (2006)

## Mention two factors on which the resistance of a wire depends.

## (2006, 2010)

## State whether the resistivity of a wire changes with the change in the thickness of the wire.

## (2018)

## Which particles are responsible for current in conductors?

## (2017)

## The relationship between the potential difference and the current in a conductor is stated in the form of a law. Name the law.

## (2015)

## What is an Ohmic resistor?

## (2014)

## Two copper wires are of the same length, but one is thicker than the other.

## i) Which wire will have more resistance?

## ii) Which wire will have more specific resistance?

## (2014)

## State Ohm's law.

## (2009, 2013)

## A metal wire of resistance 6Ω is stretched so that its length is increased to twice its original length. Calculate its new resistance.

## (2013)

## A cell is sending current in an external circuit. How does the terminal voltage compare with the e.m.f of the cell?

## (2013)

## Write an expression for the electrical energy spent in the flow of current through an electrical appliances in terms of I, R and t.

## (2012)

## What is a non-ohmic resistor?

## (2011)

## i) An electric bulb is marked 100W, 250V. What information does this convey?

## ii) How much current will the bulb draw if connected to a 250V supply?

## (2011)

## Calculate the quantity of heat that will be produced in a coil resistance 75 Ω if a current of 2A is passed through it for 2 minutes.

## (2010)

## A substance has nearly zero resistance at a temperature of 1K. What is such a substance called?

## (2010)

## Diagrammatically illustrate how you would connect a key, a battery, a voltmeter, an ammeter, an unknown resistance R and a rheostat so that it can be used to verify the above law.

## (2009)

## Find the cost of operating an electric toaster for tow hours, if it draws 8A current on a 110 volt circuit. The cost of electrical energy is Rs. 2.50 per kWh.

## (2006)

##

## DIAGRAM BASED QUESTIONS

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