Question

An electric iron draws a currunt of 3.4 amphere from the 220 volt supply line.what currunt will this electric iron draws when connected to 110 volt supply line.

Answer 1

say the current is $i$ when connected to $110V$ supply, setup a proportion using ohm's law and solve $i$
$\dfrac{3.4}{220}=\dfrac{i}{110}$

$i=1.7A$

Answer 2

I = 3.4 Amp
V = 220 Volts

Electric iron has a resistance = R

  V = I R
       => R = V / I = 220 / 3.4
                = 64.7  Ω
  
 When the electric iron is connected to a 110 Volts supply,
       I = V / R = 110 / 64.7 = 1.7 Amp.

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Alternately,  As the voltage becomes  half of its value, the current becomes half of its value, as  the current is directly proportional to the potential difference across a conductor or a resistor.    This is as per Ohm's law.