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A student made an electric circuit shown here to measure the current through two lamps.
A. Are the lamps in series or parallel?
B. The student has made a mistake in this circuit.
What is the mistake?
C. Draw a circuit diagram to show the correct way to connect the circuit.
Use the proper circuit symbols in your diagram.
An electric circuit consisting of a 0.5 m long nichrome wire XY, an ammeter, a voltmeter, four cells of 1.5 V each and a plug key was set up.
(i) Draw a diagram of this electric circuit to study the relation between the potential difference maintained between the points 'X' and 'Y' and the electric current flowing through XY.
(ii) Following graph was plotted between V and I values:
What would be the value of ratios when the potential differences us 0.8 V, 1.2 V and 1.6 V respectively?
What conclusion does you drawn from the values?
(iii) What is the resistance of the wire?
The values of potential difference V applied across a resistor and the corresponding values of current I flowing in the resistor are given below :
Potential difference, V (in volts):
Current, I (in amperes)
Plot a graph between V and I, and calculate the resistance of the resistor.
The electrical resistivities of five substances A, B, C, D and E are given below :
A) 5.20 x 10-8 Ω m
B) 2.60 x 10-8 Ω m
C) 10.0 x 10-8 Ω m
D) 1.70 x 10-8 Ω m
(a) Which substance is the best conductor of electricity? Why?
(b) Which one is better conductor: A or C? Why?
(c) Which substance would you advice to be used for making heating elements of electric irons? Why?
(d) Which two substances should be used for making electric wires? Why?
An electric bulb of resistance 20Ω and a resistance wire of 4 Ω are connected in series with a 6 V battery. Draw the circuit diagram and calculate:
(a) total resistance of the circuit
(b) current through the circuit.
(c) potential difference across the electric bulb.
(d) potential difference across the resistance wire.
Two resistors, with resistances 5 Ω and 10 Ω respectively are to be connected to a battery of emf 6 V so as to obtain:
(i) minimum current flowing
(ii) maximum current flowing
(a) How will you connect the resistances in each case?
(b) Calculate the strength of the total current in the circuit in the two cases.
An electric heater which is connected to 220 V supply line has two resistance coils A and B of 24 Ω resistance each. These coils can be used separately (one at a time), in series or in parallel. Calculate the current drawn when:
(a) only one coil A is used.
(b) coils A and B are used in series
(c) coils A and B are used in parallel.
A 5 V battery is connected to two 20 Ω resistors which are joined together in series.
(a) Draw a circuit diagram to represent this. Add an arrow to indicate the direction of conventional current flow in the circuit.
(b) What is the effective resistance of the two resistors?
(c) Calculate the current that flows from the battery.
(d) What is the p.d. across each resistor?
The figure given below shows an electric circuit in which current flows from a 6V battery through two resistors.
(a) Are the resistors connected in series with each other or in parallel?
(b) For each resistor, state the p.d. across it.
(c) The current flowing from the battery is shared between the two resistors. Which resistor will have bigger share of the current
(d) Calculate the effective resistance of the two resistors.
(e) Calculate the current that flows from the battery.
Ten bulbs are connected in a series circuit to a power supply line. Ten identical bulbs are connected in a parallel circuit to an identical power supply line.
(a) Which circuit would have the highest voltage across each bulb?
(b) In which circuit would the bulbs be brighter?
(c) In which circuit, if one bulb blows out, all others will stop glowing?
(d) Which circuit would have less current in it?
Consider the circuit given below where A, B and C are three identical light bulbs of constant resistance.
(a) List the bulbs in order of increasing brightness.
(b) If C burns out, what will be the brightness of A now compared with before?
(c) If B burns out instead, what will be the brightness of A and C compared with before?
The table below shows the current in three different electrical appliances when connected to the 240 V mains supply:
(a) Which appliance has the greatest electrical resistance? How does the data show this?
(b) The lamp is connected to the mains supply by using a thin, twin-cored cable consisting of live and neutral wires. State two reasons why this cable should not be used for connecting the kettle to the mains supply.
(c) Calculate the power rating of the kettle when it is operated from the 240 V mains supply.
(d) A man takes the kettle abroad where the mains supply is 120 V. What is the current in the kettle when it is operated from the 120 V supply?
A boy noted the readings on his home’s electricity meter on Sunday at 8 AM and again on Monday at 8 AM (see Figures below).
(a) What was the meter reading on Sunday ?
(b) What was the meter reading on Monday?
(c) How many units of electricity have been used ?
(d) If the rate is Rs. 5 per unit, what is the cost of electricity used during this time?
The electrical resistivities of four materials P, Q, R and S are given below :
P - 6.84 × 10-8 Ω m
Q - 1.70 × 10-8 Ω m
R - 1.0 × 1015 Ω m
S - 11.0 × 10-7 Ω m
Which material will you use for making:
(a) heating element of electric iron
(b) connecting wires of electric iron
(c) covering of connecting wires? Give reason for your choice in each case.
Two exactly similar heating resistances are connected (i) in series, and (ii) in parallel, in two different circuits, one by one. If the same current is passed through both the combinations, is more heat obtained per minute when they are connected in series or when they are connected in parallel? Give reason for your answer.