CBSE Class-X
Subject – Science
Topic- Electric Current & and Its Effect

 (Q.1) A man has five resistors each of value 0.2 ohms. The maximum resistance he can obtain by connecting them will be ( 1 mark )
(a) 0.1 ohm
(b) 1.0 ohm
(c) 0.04 ohm
(d) 0.4 ohm

(Q.2) In a circuit the current flowing through a resistor is 1 Ohm per second. The heat generated in the 4 ohm resistor is ( 1 mark )
(a) 2 cal/s
(b) 3 cal/s
(c) 4 cal/s
(d) 10cal/s

(Q.3) What is electric current? ( 1 mark )

(Q.4) What is the SI unit of electric current? ( 1 mark )

(Q.5) What is the SI unit of electric charge? ( 1 mark )

(Q.6) Which metal is the best conductor of electricity at room temperature? ( 1 mark )

(Q.7) Why are metals able to conduct electricity? ( 1 mark )

(Q.8) How should the resistances be connected so that the equivalent resistance is increased? ( 1 mark )

(Q.9) The length of the wire is doubled, what is the change in its resistively? ( 1 mark )

(Q.10) Why is tungsten used as filament in bulbs? ( 1 mark )

(Q.11) There is change in the length of the wire, will its resistance change?( 1 mark )

(Q.12) How is power related to current and voltage? ( 1 mark )

(Q.13) Range of resistively of metals and alloys is: ( 1 mark )
(a) 10-7 to 10-5 m
(b) 10-6 to 10-4 m
(c) 10-7 to 10-4 m
(d) 10-8 to 10-6 m

(Q.14) Direction of conventional current is from ( 1 mark )
(a) Negative terminal to positive terminal
(b) Positive terminal to negative terminal
(c) In any direction
(d) In both the directions

(Q.15) Electric current is defined as the ( 1 mark )
(a) Rate of flow of charges
(b) Total quantity of charges flowing through the circuit.
(c) Number of electrons flowing through the circuit.
(d) Number of ions flowing

(Q.16) S.I. Unit of current is ( 1 mark )
(a) Ampere
(b) Coulomb
(c) Volt
(d) Watt

(Q.17) Potential difference is defined as ( 1 mark )
(a) The amount of work done in moving a unit charge in a unit time
(b) Distance between two terminals
(c) Length of the connecting wire
(d) The amount of work done in moving a unit charge from one point to another.

(Q.18) S.I. Unit of potential difference is ( 1 mark )
(a) Volt
(b) Coulomb
(c) Ampere
(d) Watt

(Q.19) 1 microampere is equivalent to ( 1 mark )
(a) 6.25 x 109 electrons
(b) 6.25 x 106 electrons
(c) 6.25 x 1012 electrons
(d) 6.25 electrons

(Q.20) The length of a wire is doubled, but its cross section remains the same, then its resistance will become ( 1 mark )
(a) 4 times
(b) 2 times
(c) ½ times
(d) 8 times

(Q.21) Resistance of a conductor do not depends upon ( 1 mark )
(a) The length of the conductor
(b) Area of cross section of the conductor
(c) Material of the conductor
(d) Temperature of the conductor

(Q.22) According to Ohm’s law ( 1 mark )
(a) Current is directly proportional to the potential difference
(b) Current is inversely proportional to the potential difference
(c) Current is equal to the potential difference
(d) Current is independent of potential difference

(Q.23) Heat produced due to flow of current through a conductor is given by the formula ( 1 mark )
(a) H = I2 R t
(b) H = V I/ t
(c) H = V t / R
(d) H= It

(Q.24) 1volt= ( 1 mark )
(a) 1joule/1newton
(b) 1joule/1cm
(c) 1joule/1coulomb
(d) 1newton/1metre

(Q.25) The combined resistance of any number of resistances connected in series is equal to ( 1 mark )
(a) The sum of individual resistances
(b) The sum of reciprocals of individual resistances
(c) Product of individual resistances
(d) Highest individual resistance

(Q.26) The reciprocal of the combined resistance of any number of resistances connected in parallel is equal to ( 1 mark )
(a) The sum of reciprocals of individual resistances
(b) Reciprocal of the product of individual resistances
(c) Reciprocal of sum of all the resistances
(d) Sum of individual resistances

(Q.27) When two or more resistors are connected in series ( 1 mark )
(a) The current passing through each resistor is same
(b) The potential difference across each resistor is same
(c) Current is inversely proportional to the potential difference
(d) Potential difference and current are independent

(Q.28) When two or more resistors are connected in parallel ( 1 mark )
(a) The current passing through each resistor is same
(b) The potential difference across each resistor is same
(c) Current and potential are inversely proportional
(d) Current increases linearly

(Q.29) Commercial unit of electrical energy is ( 1 mark )
(a) Joule
(b) Coulomb
(c) Watt
(d) k W h

(Q.30) The work done in moving a charge of 3 C across two points having potential difference 20V ( 1 mark )
(a) 40J
(b) 60J
(c) 80J
(d) 100J

(Q.31) Power rating of an electric appliance indicates ( 1 mark )
(a) The rate of consumption of electrical energy.
(b) Amount of heat evolved.
(c) Brightness of the light.
(d) Quality of the appliance.

(Q.32) One kilowatt hour = ( 1 mark )
(a) 3.6 x 106 J
(b) 3.6 kJ
(c) 1000 watt
(d) 3.6 x 106 calories

(Q.33) What happens to the heating effect when the direction of current is reversed? ( 1 mark )
(a) Cooling effect is observed
(b) Amount of heat remains unchanged
(c) There will be a short circuit
(d) Current will increase suddenly

(Q.34) Alloys are usually used in electrical heating devices because ( 1 mark )
(a) Resistively of an alloy is generally higher than that of constituent elements.
(b) Alloys oxidize readily at high temperature.
(c) Alloys are bad conductor of heat
(d) Alloys do not have free electrons

(Q.35) An electric bulb of 40 W is connected to a source of 220 V, the current drawn by the bulb will be ( 1 mark )
(a) 0.18 A
(b) 18 A
(c) 1.8 A
(d) 180 A

(Q.36) Electrical energy consumed in lighting an electrical bulb of 60 W for 5 hours is ( 1 mark )
(a) 3 kWh
(b) 1.08 x 106 J
(c) 5KWh
(d) 2.03 x 106 J

(Q.37) What is the melting point of tungsten? ( 1 mark )
(a) 30500C
(b) 35780C
(c) 33800C
(d) 38500C

(Q.38) Difference of electric pressure is called: ( 1 mark )
(a) Electric difference
(b) Potential difference
(c) Charge difference
(d) Volt difference

(Q.39) An electric iron consumes energy at a rate of 840W when it is connected to a source of voltage 220V. The current flowing is ( 1 mark )
(a) 3.81A
(b) 3A
(c) 2A
(d) 1.4A

(Q.40) What is the minimum resistance that can be obtained using three 5 ohm resistors? ( 1 mark )
(a) 5 ohm
(b) 1.6 ohm
(c) 15 ohm
(d) 1 ohm

(Q.41) A refrigerator rated 400W operates 8hour per day. The total number of commercial units for 30days will be ( 1 mark )
(a) 96
(b) 46
(d) 100

(Q.42) What is ohm’s law? Give its mathematical expression? ( 2 Marks )

(Q.43) How much current will an electric heater coil draw from a 220 volt line, if the resistance of the heater coil is 40 ?( 2 Marks )

(Q.44) Calculate the number of electrons constituting one coulomb of charge. ( 2 Marks )

(Q.45) The combination of resistances shown below has equivalent resistance equal to 12 ohm, what is the value of R?(2Marks )

(Q.46) Calculate the amount of charge that would flow in 1 hour through the elements of an electric bulb drawing a current of 0.4 A. ( 2 Marks )

(Q.47) What is the power of an electric lamp, if it draws 20 A current when connected to 220 V line? ( 2 Marks )

(Q.48) The potential difference between the terminals of an electric heater is 30 volt when it draws current of 4 A from the source. What current will the heater draw if the potential difference is increased to 120 volt? ( 3 Marks )

(Q.49) A current of 4 A exists in a 10 resistor for 4 minute. Find the charge and the number of electrons that pass through any cross-section of the resistor in this time. ( 3 Marks )

(Q.50) A 100 watt electric bulb is lighted for 2 hours daily and four 40 watt bulbs are lighted for 4 hours daily. Calculate the electric energy consumed in kwh in 30 days. ( 3 Marks )

(Q.51) Two lamps, one rated 100 W at 220 volts and the other 60W at 220 volts are connected in parallel to a 220 V supply. What current is drawn from the supply line? ( 3 Marks )

(Q.52) To produce 1000 joule of heat in 10 seconds, how much voltage should be applied to 50 resistance. ( 3 Marks )

(Q.53) In the circuit diagram given below, find the equivalent resistances and total current flowing through the circuit.(3Marks )

(Q.54) a) State the law, which relates the current in a conductor to the potential difference across its ends.

b) Draw the V-I graphs for a
(i) Metallic conductor.
(ii) Liquid Electrolyte.
(iii) Vacuum tube.

c) A simple electric circuit has 24 V batteries and a resistor of 30 ohm. What will be the current in the circuit? ( 5 Marks )