Physics!! pls help me!!!!!?

Question

1.Can eight 1.5V cells arranged in series can start a car engine?
Explain ur answer.

2.If a battery is fresh,the voltage across the load is almost equal to the e.m.f of the battery.After the battery has been used,its terminal voltage decreases.Explain this observation.
Pls explain what is terminal voltage,is it same with the voltage of the external circuit?

3.Pls calculate....two 1.5 V dry cells are connected in series into the barrel of a flashlight.The internal resistance of the cell are 4.0 ohm and 0.6 ohm.When the flashlight is switched on,a current of 0.5A flows through the bulb.What is the resistance of the bulb?
p/s:The answer stated in my book is 2ohm....and i dunno how to get the answer as i got 5 ohm...confused???

Answer 1

1. If you are trying to connect 8 small dry cells to make a 12V, car battery, I am afraid you won't succeed. True the voltage will be 12V but the current capacity (expressed as AH, Ampere Hours) of the dry cells is very small and cannot supply the massive current needed to start the car engine.

2. The internal resistance of a fresh battery is quite low and so the voltage across the terminals is almost same as the rated emf. Terminal voltage is what you measure with a voltmeter by connecting its leads to the positive and negative terminals of the battery.
After the battery has been used for some time, the internal resistance of the battery goes up and thus part of the emf is dropped across the battery itself and the terminal voltage drops. If we ignore the electric resistance of the copper wires (leads), we can consider the terminal voltage as equal to the voltage applied to the external circuit.

3. Let r be the resistance of the bulb. Total resistance of the circuit is 4 + 0.6 + r Ohms and current flowing through the circuit is given as 0.5 A.

EMF of the two cells = 3 V

3 / 0.5 = 6 ohms is the total resistance (R = V/I)

4.6 + r = 6 or r = 6 - 4.6 = 1.4 ohms

r = resistance of the flash bulb = 1.4 ohms

The answer given in the book is also not correct as you can see.

Answer 2

1.! battery containing 8 cells =12v
1 flashlight containing 8x1.5v cells =12 volts but the smaller battery's wont start a car.
A battery w/ 8x1.5v will start a car if it has enough amperage.
The terminal voltage is measured at the source (battery) the rest is not .Therefore there will be a different measurement even just through the copper wire.
E=IxR

Answer 3

Sound wave is noted as longitudinal wave as a results of fact it travels longitudinally interior the direction to the propagation of the wave.this is a mechanical wave. to offer sound wave there needs a disturbance. such as you notice the waves interior the river or interior the sea that's as a results of air flowing at its floor or as a results of interior disturbance.with the purpose to declare, whilst there's a reason there is an result. right here Air or inner disturbance is the reason and the end result's the wave.in addition once you strike, as an occasion, strike a metallic pie at its one end and you pay attention the sound at its different end very actually.The traveling mode of those waves are longitudinal.To make nevertheless extra, take a chew of wood of which the mid area of this is vertically slit.bypass a protracted piece of thread with the aid of this slit.carry the single end of the string and the different end additionally some physique to hold it. Now get somebody to hold the slit- wood vertically.The string must be particularly taut .Now the two of one of who's conserving the string can flow his hand up & down so as that the string(Thread) starts off shifting up and down.Now you will see the vibration of the string with waves traveling interior the direction of the slit longitudinally.comparable is the case with sound wave. i think of the occasion makes you sparkling how does sound wave propagate.thank you on your question.be conscious: Sound needs medium to trip.It won't be able to trip in vacuum.