Direct current in electric motors?

AI Thread Summary
Small electric motors with a single armature loop can become stuck due to a lack of current flow when the brushes reach the split in the commutator ring, preventing the motor from starting independently. A slight twist of the armature can close the circuit, allowing the motor to operate again. To mitigate this issue in DC brushed motors, using multiple armature loops can help maintain current flow and prevent stalling. Understanding these principles is crucial for effective troubleshooting and motor design. Overall, addressing the design and operational aspects can enhance the reliability of small electric motors.
Plasm47
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1. Small electric motors with only one armature loop sometimes get stuck. They can be started again by giving the armature a small twist. Looking at the diagram below, what might be the explanation for the motor not being able to start on its own?
bOIVO.jpg


When the brush(es) reaches the split within the ring, current ceases to flow. This lack of electricty will stop the split ring commutator and evidently, the motor. Since no current can be transmitted, the motor can't start on its own. However, giving the armature a small twist will close the circuit allowing the motor to operate.

Please help! I'm not really understanding the principles of motors. I'm taking shots in the dark in answering my questions.
 
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Plasm47 said:
1. Small electric motors with only one armature loop sometimes get stuck. They can be started again by giving the armature a small twist. Looking at the diagram below, what might be the explanation for the motor not being able to start on its own?
bOIVO.jpg


When the brush(es) reaches the split within the ring, current ceases to flow. This lack of electricty will stop the split ring commutator and evidently, the motor. Since no current can be transmitted, the motor can't start on its own. However, giving the armature a small twist will close the circuit allowing the motor to operate.

Please help! I'm not really understanding the principles of motors. I'm taking shots in the dark in answering my questions.

Your answer is fine. Can you think of some things that could be done to minimize this problem with DC brushed motors?
 
berkeman said:
Your answer is fine. Can you think of some things that could be done to minimize this problem with DC brushed motors?

The problem can be minimize by using more than one armature
 
Plasm47 said:
The problem can be minimize by using more than one armature

Good answer! :smile:
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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