? asked in Science & MathematicsPhysics · 9 years ago

Ohm's law and electric currents problem? Please help!?

A 47Ω resistor can dissipate up to 0.22 W of power without burning up. What is the smallest number of such resistors that can be connected in series across a 9.0 V battery without any one of them burning up?

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  • 9 years ago
    Favorite Answer

    P = E²/R

    for one resistor

    0.22 = E²/47

    E = 3.22 volts

    9v / 3.22v = 2.80

    so the answer is 3.

    Check:

    they will have 3 volts across them

    P = 9/47 = 0.191 watts OK.

  • rigel
    Lv 4
    4 years ago

    R = E / I, sparkling up for R A = rho * L / R you know the resistivity of copper (a million.sixty 8×10?8), you know the dimensions, and by fixing the formula above, you are going to know what the area must be. area = pi * r^2, sparkling up for r

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