1Which of the V against I graphs shows Ohm's law: A (falling straight line), B (rising curve), C (straight line through the origin) or D (falling curve)?
2What is the heating element of an electric heater made of: copper, constantan, tungsten or nichrome?
3Why are loads in a household circuit connected in parallel: to send equal current through all, to keep all at the same potential difference, to keep resistance unchanged, or to increase resistance?
4Bulb A is marked 220 V, 0.5 A and bulb B 220 V, 0.45 A. Working at full capacity, which is true: B uses more per hour than A; A changes more energy per second than B; B produces more heat per second than A; using B more than A raises the bill?
5In a series circuit, R and a 6 Ω resistor have 6 V and 3 V across them. What is R: 6 Ω, 12 Ω, 18 Ω or 24 Ω?
6How much energy does a 1 kW heater change in 1 hour: \( 3.6 \times 10^{5} \) J, \( 3.6 \times 10^{4} \) J, \( 3.6 \times 10^{3} \) J or \( 3.6 \times 10^{6} \) J?
7Write the difference between electromotive force and potential difference.
8Write the difference between series connection and parallel connection of loads.
9Give a reason: a bulb glowed brighter with a group of two dry cells than with one cell.
10Give a reason: nichrome wire is used in heaters.
11Give a reason: loads in a household circuit are connected in parallel.
12Define electric current.
13What is electromotive force? Is it really a force like other forces? Explain.
14What does 1.5 V written on a dry cell mean?
15State Ohm's law and show that V = IR.
16What is electrical resistance? Define 1 Ω.
17Of a thick wire and a thin wire of the same length, which has more resistance?
18What is the heating effect of electric current? Name two appliances based on it.
19What is electric power? What does 6 W written on a mobile phone mean?
20Suraj removed one bulb from a set of bulbs on a 3 V battery, reconnected the rest, and found they glowed brighter. How were the bulbs connected? Describe the circuit and give the reason.
21You have two identical bulbs, two dry cells and wires. How would you connect them for the brightest light, and why?
22How long does it take for 0.2 C of charge to flow through a wire carrying 10 mA?
23A wire carries 5 mA. How much charge flows through it in 1 minute?
24A torch bulb is marked 3 V, 500 mA. Find its resistance and power.
25A room on a 220 V supply has a 1100 W heater and an 11 W CFL on. Ignoring the wires' resistance, find the current through each and each one's resistance.
26A kettle's label reads 220 to 240 V and 2520 to 3000 W. On a 220 V supply, what is its largest current? If the water boils in 4 minutes, what is the most it uses in units?
27A house runs ten 7 W LEDs for 6 hours a day, a 150 W TV for 8 hours a day, four 150 W fans for 10 hours a day and a 750 W iron for 40 minutes a week. Find the monthly consumption and, at Rs. 10 a unit, the monthly bill.
28What is the commercial unit of electricity consumption? Show how many joules are in 1 kWh.
29A meter read 4520.5 last month and 4610.5 this month. At Rs. 12 per unit, what is the bill?
30Why does running one heater instead of two lower a bill? Explain using P × n × t.