Qualification > Sciences
physics help !!
nid404:
--- Quote from: QuickSilver on June 09, 2009, 09:15:43 am ---Voltage Decreases because voltage is the pressure basically, so if there is less resistance then this means that ekectrons will produce a less effort to pass through decreasing the pressure, and since Voltage is INVERSLY proportional to current, then when voltage decreases this casuses the current to increase causing the motor to spin faster
Right Sir??
Thanks
--- End quote ---
that is what i thought but the mark scheme says the motor stops... ???
astarmathsandphysics:
--- Quote from: nid404 on June 09, 2009, 09:10:44 am ---but astar how is the pd decreasing, cuz the current is increasing( resistance is reduced.) And when the current increases rotation in a motor is faster no?? Plz explain astar...i too am giving my exam tomorrow
--- End quote ---
The voltage a cross the motor is the voltage across that part of the resistor between X and th other wire connecting the motor to the circuit. If you move the conact at x to the bottom of the resistor this voltage will be zero and the current and voltage and resistance in the circuit is irrelevant. Hence the motor stops
QuickSilver:
--- Quote from: astarmathsandphysics on June 09, 2009, 09:18:31 am ---
--- Quote from: nid404 on June 09, 2009, 09:10:44 am ---but astar how is the pd decreasing, cuz the current is increasing( resistance is reduced.) And when the current increases rotation in a motor is faster no?? Plz explain astar...i too am giving my exam tomorrow
--- End quote ---
The voltage a cross the motor is the voltage across that part of the resistor between X and th other wire connecting the motor to the circuit. If you move the conact at x to the bottom of the resistor this voltage will be zero and the current and voltage and resistance in the circuit is irrelevant. Hence the motor stops
--- End quote ---
ohh so ok V and I are inversely proporional but when V=0 (zero), then no current can occur right??
Kim:
their is this question in may 2007 no 3 cud sum 1 explain the answer to me?
nid404:
--- Quote from: astarmathsandphysics on June 09, 2009, 09:18:31 am ---
--- Quote from: nid404 on June 09, 2009, 09:10:44 am ---but astar how is the pd decreasing, cuz the current is increasing( resistance is reduced.) And when the current increases rotation in a motor is faster no?? Plz explain astar...i too am giving my exam tomorrow
--- End quote ---
The voltage a cross the motor is the voltage across that part of the resistor between X and th other wire connecting the motor to the circuit. If you move the conact at x to the bottom of the resistor this voltage will be zero and the current and voltage and resistance in the circuit is irrelevant. Hence the motor stops
--- End quote ---
ok so when V is 0, rest pf the things are not to be considered..so now i understand that the resistor is acting like a potential divider.
thanks sir
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