Effects of Electric Current
(b) Two electric bulbs rated 100 W; 220 V and 60 W; 220 V are connected in parallel to electric mains of 220 V. Find the current drawn by the bulbs from the mains.
(b) Study the following circuit and find out:
(i) Current in 12 Ω resistor.
(ii) The difference in the readings of A1 and A2, if any.
Compare the power used in 2 Ω resistor in each of the following circuits:
A bulb is rated 40 W; 220 V. Find the current drawn by it, when it is connected to a 220 V supply. Also find its resistance. If the given bulb is replaced by a bulb of rating 25 W; 220 V, will there be any change in the value of current and resistance? Justify your answer and determine the change.
Derive the expression for the heat produced due to a current ‘I’ flowing for a time interval ‘t’ through a resistor ‘R’ having a potential difference ‘V’ across its ends. With which name is the relation known? How much heat will an instrument of 12W produce in one minute if it is connected to a battery of 12V?
Explain with the help of a labelled circuit diagram how you will find the resistance of a combination of three resistors, or resistance R1, R2 and R3, joined in parallel. Also mention how you will connect the ammeter and the voltmeter in the circuit when measuring the current in the circuit and the potential difference across one of the three resistors of the combination.
A lamp rated 100 W at 220 V is connected to the mains electric supply. What current is drawn from the supply line if the voltage is 220 V?
Two lamps, one related 60 W at 220 W at 220 V and the other 40 W at 220 V, are connected in parallel to the electric supply at 220 V.
(a) Draw a circuit diagram to show the connections.
(b) Calculate the current drawn from the electric supply.
(c) Calculate the total energy consumed by the two lamps together when they operate for one hour.
(a) Distinguish between the terms “overloading and short circuiting” as used in domestic circuits.
(b) Why are the coils of electric toasters made of an alloy rather than a pure metal?
An electric iron has a rating of 750 W, 220 V. Calculate
(i) current passing through it, and
(ii) its resistance, when in use
An electric heater is used on 220 V supply and takes a current of 3.4 A. Calculate (i) its power and (ii) its resistance, when it is in use.
An electric lamp is marked 100 W, 220 V. It is used for 5 hours daily. Calculate
(i) its resistance while glowing
(ii) energy consumed in kWh per day
A torch bulb is rated 2.5 V and 750 mA. Calculate (i) its power, (ii) its resistance and (iii) the energy consumed if this bulb is lighted for four hours.
A torch bulb is rated 5.0 V and 500 mA. Calculate (i) its power, (ii) resistance and (iii) energy consumed when it is lighted for four hours.
(a) Draw a schematic labelled diagram of a domestic wiring circuit which includes (i) a main fuse (ii) a power meter, (iii) one light point, and (iv) a power plug.
(b) Why is it necessary to connect an earth wire to electric appliances having metallic covers?
A torch bulb is rated 3.0 V and 600 mA. Calculate: (i) its power, (ii) its resistance and (iii) the energy consumed if it is lighted for 4 hours.