Question

Pls help with all questions

a) A charged particle travels undeflected through perpendicular electric and magnetic fields whose magnitudes are 4000 N/C and 20mT, respectively. Find the speed of the particle if it is an alpha particle. (Alpha particle is a helium nucleus-a positive ion with a double positive charge of +2e.) I don't understand how the answer is v= 2.0*10^5 m/s. How could the velocity be independent of the charge since v = F / qBsinθ and q =2e? Should the answer be v = 1.0*10^5 m/s?

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b) Ip= 19A at Vp = 440V and Vs= 9000V. If the transformer is 95% efficient, how many turns are in the secondary coil? (efficiency e is the ratio of the power output to the power input or e = Ps/Pp). I know the result is Ns= (Vs Np) / Vp = 3680 turns, but why can't I use this below equation:

Ps/Pp = (Is Vs) / (Ip Vp) = 0.95 (1)

Is/Ip = Np/Ns

plug in Np/Ns into (1), we have Np Vs / Ns Vp = 0.95

Ns= (Vs Np) / (0.95 Vp)

So why can't I use this equation [ Ns= (Vs Np) / (0.95 Vp) ] to find secondary coil.

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c) a 240-V dc motor has an armature whose resistance is 1.8 ohms. When running at its operating speed, it draws a current of 14.0 A. Starting current is 133 A. What series resistance would be required to limit the starting current to 26.0 A? Could you please draw a diagram of this case. Please explain why I = 240V / (R + r) ? Where does r come from and what formula is this?

Answer 1

i am able to answering only first question as per Chegg guidelines...if u want other one send individual i am happy to help...