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  1. #1
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    questions in physics help

    1 – What is the relation between the main current which flows from the source and the current in each resistor in series ?
    The current is same for each resistor in series

    2 – What is the relation between the potential difference across the source and the potential differences across each resistor in series ? Which resistor has the highest pd across it ?
    potential difference will divide for each resistor in series
    the highest pd highest. .. which has lees are


    3- A potential difference of 12 V is found to produce a current of 0.40 A in a 3.2 cm length of wire with a uniform radius of 0.40 cm what is the resistance and resistively of wire ?R= V/I
    = 12 / 0.40 = 30 Ω

    4 – A 3Ω resistor a 6 Ω resistor and 9 Ω resistor are connected in series with a 12 V battery .
    Draw a circuit diagram . What are
    A ) the equivalent resistance
    b) the current in each resistor
    c ) the pd across each resistor



    A) R = R1 + R2 + R3
    18 Ω

    B ) I = V/R = 18/12 =1.5 A

    C ) V= IR
    = 1.5 X 18 == 27
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by r-soy View Post
    1 – What is the relation between the main current which flows from the source and the current in each resistor in series ?
    The current is same for each resistor in series

    2 – What is the relation between the potential difference across the source and the potential differences across each resistor in series ? Which resistor has the highest pd across it ?
    potential difference will divide for each resistor in series
    the highest pd highest. .. which has lees are
    Since the current $$i is the same through each resistor we have for the $$k th resistor (from Ohm'd law):

    V_k=i R_k

    that is the potential drop across each is proportional to its' resistance.

    CB
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  3. #3
    Grand Panjandrum
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    Quote Originally Posted by r-soy View Post


    3- A potential difference of 12 V is found to produce a current of 0.40 A in a 3.2 cm length of wire with a uniform radius of 0.40 cm what is the resistance and resistively of wire ?R= V/I
    = 12 / 0.40 = 30 Ω
    You are also asked for the resistivity, which in this case is:

    \displaystyle \rho=R\frac{A}{l}

    where $$A is the crossectional area of the wire and $$l is its' length.

    CB
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  4. #4
    Grand Panjandrum
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    Quote Originally Posted by r-soy View Post
    4 – A 3Ω resistor a 6 Ω resistor and 9 Ω resistor are connected in series with a 12 V battery .
    Draw a circuit diagram . What are
    A ) the equivalent resistance
    b) the current in each resistor
    c ) the pd across each resistor



    A) R = R1 + R2 + R3
    18 Ω

    B ) I = V/R = 18/12 =1.5 A

    C ) V= IR
    = 1.5 X 18 == 27
    A and B are OK, but C asks for the voltage drop across each resistor, so there are three voltages required, and the answer to (2) tells you their ratios and 4A their sum

    CB
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