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science-physics

class VII

#### Key Concepts

battery, circuit diagram, electric component, electric bell, electromagnet, fuse, heating effects of currents, magnetic effects of currents

#### essential questions

1. How can you get electricity to a source from a receiver?
2. What does a switch do in a circuit?
3. Can you make a magnet that turns on and off?
4. Why is the transfer of energy important?

#### Remembering:

1. A combination of two or more cells in called______ a) battery   b) Button cell   c) An electric cell  d) truck battery
2. When an electric circuit from the positive terminal of the battery to the negative terminal of the battery is complete, then the circuit is said to be:  a) closed  b) open   c) Broken  d) incomplete
3. Current flows through the circuit when the circuit is in the _____condition.  a) closed Open  b) broken  c) incomplete
4. The heat energy produced by a glowing bulb can be minimized by using _____ bulbs in place of ordinary electric bulbs. a) candle  b) CFL bulbs  c) torch  d) kerosene lamp
5. The wire which melts and breaks the circuit when large current is allowed to flow through it is called: a) a fuse wire    b) electric wire   c) connecting wire   d) filament
6. _______ piece is attracted by an electromagnet.  a) wood   b) iron   c) plastic   d) rubber
7. Who discovered that when a compass needle is kept nearer to an electric circuit in which current is flowing it deflects. a) Han Christian Oersted  b) Micheal Faraday   c) Galileo   d) Newton
8. Electric bell works on the principle a) Electrical energy is converted into mechanical energy    b) electrical energy is converted into sound energy    c) mechanical energy is converted into sound energy   d) sound energy is converted into electrical energy
9. When electric charge moves through electrical conductor, there is a production of:  a) electric current  b) electrical charge   c) electric cell    d)electric circuit
10. Measure of rate of flow of electric charge through an electrical conductor is known as: a) electric current  b) electrical charge  c) electric cell   d) electric circuit
11. If electric wires and appliances are overheated due to high voltage of electric current they can: a) catch fire  b) burn  c) freeze  d) both a and b
12. Do not use appliances, if : a) damaged   b) wires exposed   c) working properly    d) both a and b
13. A component which is used to close or break a circuit, is: a) bulb b)switch c)wire d)electric cell
14. A diagram drawn by using symbols which represents electrical components is called:  a) circuit diagram   b) current diagram  c) charges diagram  d) electric diagram
15. A short thin piece of wire which is heated up and melt by flowing of electric current in it, is called : a) circuit b) fuse c) cell  d) resistor
16. A component which provides resistance is called: a) heat   b) energy   c) product   d) resistor
17. A circuit which splits into two or more branches is called:  a) series circuit   b) parallel circuit   c) open circuit d) close circuit
18. Two or more cells when connected in series make a:  a)battery     b) circuit    c) terminal    d) resistor
19. Energy which modern gadgets, devices and machines use is : a) electrical   b) magnetic   c) thermal   d) chemical
20. In a circuit when an electric current flows in a continuous path, it is called:  a) close circuit   b) open circuit   c) hot circuit   d) blocked circuit
21. An appliance which use simple electric circuit is an:  a) electric torch  b) microwave oven  c) air conditioner   d) generator
22. SI unit for electric current is: a) joule  b) watt  c) volt  d) ampere
23. Which of the following is not a circuit element: a) Battery  b) Voltmeter  c) Potential difference  d) Resistor
24. A fuse wire is made up of alloy: a) Nichrome  b) tin- lead  c) manganin  d) constantan

Fill in the blanks:

1.   _______ is a device which controls the flow of excess current in an appliance.
2. ______happens when supply terminals touch each other.
3. ______ is a device that combines the function of a circuit and fuse.
4. MCB is based on the principle of _________ of current.

#### understanding:

1. An electric wire connected in a circular gets heated up when current is allowed to flow through it. This is due to  a) heating effect of current   b) electrical effect of current   c) musical effect of current   d) Optical effect of current
2. A glowing filament will be  a) at a low temperature  b) at a high temperature c) at room temperature  d) at the temperature of ice.
3. An electromagnet is one which behaves as a magnet when current is _______  a) allowed to flow through  b) Not allowed to flow through   c) Stopped from flowing through it
4. When the current flowing through the fuse wire exceeds the safety limit, then it will be ______ breaking the circuit. a) melted away   b) remains the same   c) damages the circuit   d) makes  the circuit remain connected
5. When electric current passes through a wire, it behaves like a magnet. This is the  a) magnetic effect of current b) electrical effect of current  c) heating effect of current  d) Optical effect of current
6. Which of the following statement is incorrect for the given circuits:                  a) Wire has no magnetic effect   b) when compass is kept near to the circuit, it will not show any deflection  c) Given circuit in incomplete because there is not source of electric energy  d) Neither P or Q
7. The magnetic field around a current carrying coil: a) last for 3 hours  b) lasts as long as current flows  c) last till its half life period  d) It is permanent

#### Application:

1. In a parallel circuit current flowing from source to each path is:  a) greater  b)lesser   c)equal   d)unequal
2. Which of the following does not work on heating effect:
3. Marking on a bulb is 60W, 220 V. What does it signify? a) Bulb is connected across 220V, 60 joules of energy s consumed for every second  b) Bulb is connected across 220V, 60 joules of energy is released  c) 60 units of current will flow in the bulb  d) 220 units of current will flow in the bulb
4. In which circuit the bulbs will glow brightly: a) In circuit P only  b) In circuit Q only  c) In both circuit P and Q only the bulbs will glow with equal brightness  d) Neither P or Q
5. Which of the following diagram represent a short circuit?
6. Which of the following circuit diagram represent given torch:
7. In the given figure there are four electromagnets. Which one is the strongest?

#### Analysis:

1. When current is passed through a conductor, the heat produced in it depends upon: Statement 1: The material of the conductor  Statement 2: The current flowing through the conductor  Statement 3: The time for which the current flows: a) Only 1 and 2   b) Only 1 and 3  c) Only 2 and 3  d) All of them
2. When the strength of the current flowing through a coil is increased. Which of the following statement is correct for it:  Statement1: Strength of magnetic field decreases Statement 2: Strength of magnetic field increases  Statement 3: Amount of heat generated due to resistance decreases  Statement 4: Strength of magnetic field remains constant
3. Observe the given circuit diagram X and Y identify the correct statement.                                                                                                                        a) Circuit Y is a series circuit  b) Bulb 2 in circuit X will glow even closed  c) In circuit Y, bulb 3 will glow if only switch S2 is closed  d) Both circuits X and Y are parallel circuits
4. Read the given statement and select the correct option: Statement1: In a circuit, surface of the bulb becomes warmer than the connecting wires when the same current flows through them  Statement 2: A thin and long wire has higher resistance than a thick and short wire. Choose the correct options: a) Both statement 1 and statement 2 are correct and statement 2 is correct explanation of statement 1.   b) Both statement 1 and Statement 2 are correct and statement 2 is not the correct explanation of statement 1. c) statement 1 is correct and statement 2 is false. d) statement 1 is false and statement 2 is correct
5. Give reasons when and why:

a) a person touches live wire by mistake, might get a fatal shock.

b) A person might get electric shock by merely touching the chassis of an electrical gadget.

c) The MCB automatically changes to off position to trips.