Use the standard symbols shown in the chapter for each circuit component.
Use the standard circuit symbols: a straight line for connecting wire; a break in the line with an open key for a switch in OFF position; a circle with a filament mark for a bulb; one long and one short parallel line for a cell; a closed key for a switch in ON position; and two or more cells joined in series for a battery.
Replace each real component in Fig. 10.21 by its circuit symbol while keeping the same single-loop connection.
Draw a simple series circuit: one cell, a switch/key and a bulb connected in a closed loop by wires. Use the cell symbol, bulb symbol and closed-switch symbol in place of the actual components.
A battery is made by connecting cells in series, positive terminal to negative terminal successively.
Connect the + terminal of the first cell to the - terminal of the second cell, the + terminal of the second cell to the - terminal of the third cell, and the + terminal of the third cell to the - terminal of the fourth cell. The free - terminal of the first cell and the free + terminal of the fourth cell become the two terminals of the battery.
Cells must be connected in series as + to -, not + to +.
The problem is that the two cells are connected positive-to-positive. Reverse one cell or change the connection so that the positive terminal of one cell is connected to the negative terminal of the other. Then complete the circuit through the switch and bulb; the bulb will glow.
Two effects of electric current are the heating effect and the magnetic effect.
A current-carrying wire behaves like a magnet and produces a magnetic field around it. This magnetic field affects the compass needle, so the needle is deflected from its north-south position.
A current-carrying wire behaves like a magnet and affects a nearby compass needle.
Yes. When the switch is closed, current flows through the wire/coil near the compass. The magnetic effect of the current deflects the compass needle.
(a) positive
(b) battery
(c) becomes hot
(d) fuse
Cells in a battery are connected positive to negative. Excess current heats and melts the fuse wire. An electromagnet attracts iron, and an electric bell uses an electromagnet.
(a) F
(b) T
(c) F
(d) T
No. An electromagnet attracts magnetic materials such as iron, but plastic is non-magnetic. Therefore it cannot be used to separate plastic bags from garbage.
No. A fuse is a safety device made of wire that melts when current exceeds a safe limit, breaking the circuit. An ordinary wire may not melt at the right current and can cause overheating, damage or fire.
Check every part of the circuit: cell placement, wire contacts, switch contact and bulb condition.
Possible defects are: the cells may be placed wrongly in the holder, the terminals may not be connected properly, the switch may not be making contact, the bulb may be fused, or a wire connection may be loose or broken.
An open switch breaks the circuit; when closed, current is established through the whole circuit almost simultaneously.
(i) No bulb will glow when the switch is OFF because the circuit is open.
(ii) When the switch is ON, current reaches all parts of the circuit almost instantly, so the bulbs glow at practically the same time.
- a. 1 A
- b. 3 A
- c. 5 A
- d. all of these
Current = power / voltage = 1000 W / 220 V ≈ 4.55 A. The fuse should be just above the working current, so 5 A is suitable.
(iii) 5 A