Poynting vector - 2024 ACF Winter

Question

The strength of radiation pressure equals the magnitude of this vector quantity over the speed of light. For 10 points each:

[10m] Name this vector quantity that represents the energy flux of an electromagnetic field. It equals the cross product of the E- and H-fields.

ANSWER: Poynting vector [prompt on S]

[10h] The Poynting vector was independently discovered by this scientist, who names a set of conditions to reduce distortion in transmission lines. He also derived the telegrapher’s equations and coined the term “impedance.”

ANSWER: Oliver Heaviside [accept Heaviside conditions]

[10e] The first telegrapher’s equation relates the spatial derivative of voltage to this quantity and its time derivative. By Ohm’s law, voltage equals this quantity times resistance.

ANSWER: current [prompt on I]

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Summary


2024 ACF Winter at Lehigh	2024-11-16	Y	7	14.29	100%	43%	0%
2024 ACF Winter at Northwestern	2024-11-16	Y	9	14.44	100%	44%	0%
2024 ACF Winter at Ohio State	2024-11-16	Y	9	14.44	100%	44%	0%
2024 ACF Winter at Online	2024-11-16	Y	7	10.00	86%	14%	0%
2024 ACF Winter at Central Florida	2024-11-16	Y	4	17.50	100%	75%	0%
2024 ACF Winter at Oxford	2024-11-16	Y	8	16.25	88%	50%	25%

Data


Rowan A	Bard A	0	0	10	10
Rutgers A	Johns Hopkins B	0	0	10	10
Penn A	Penn B	10	0	10	20
Columbia A	Penn State A	10	0	10	20
Rutgers C	Penn State B	0	0	10	10
Purdue A	Indiana A	10	0	10	20
Miami	UIUC D	0	0	10	10
Notre Dame	Northwestern A	0	0	10	10
SIUE A	Purdue B	0	0	10	10
WashU C	Purdue C	0	0	10	10
Indiana B	UChicago D	0	0	10	10
UIUC A	UChicago C	10	0	10	20
UIUC B	WashU B	10	0	10	20
UChicago B	UIUC C	10	0	10	20
Columbia B	Johns Hopkins A	0	0	10	10
Princeton A	Haverford A	10	0	10	20
CWRU A	Ohio State C	10	0	10	20
Kenyon A	CWRU C	0	0	10	10
Kenyon B	CWRU D	0	0	10	10
Michigan C	CWRU B	0	0	10	10
Michigan D	Michigan State C	0	0	10	10
Michigan State A	Pitt A	10	0	10	20
Michigan State B	Pitt B	10	0	10	20
Michigan A	Ohio State A	10	0	10	20
Ohio State B	Michigan B	0	0	10	10
Texas C	Colorado College	0	0	10	10
Iowa	Missouri	0	0	0	0
Mississippi State	Central Oklahoma	0	0	10	10
Oregon State	McGill E	0	0	10	10
NYU B	WUSTL A	0	0	10	10
Texas A	Vassar A	10	0	10	20
Florida Tech A	UF D	10	0	10	20
UCF A	Florida State University A	10	0	10	20
UF B	UCF B	10	0	10	20
UF E	UF F	0	0	10	10
Cambridge A	Bristol A	10	10	10	30
Imperial A	Cambridge B	10	10	10	30
Cambridge C	Manchester	10	0	10	20
Southampton A	Cambridge D	0	0	10	10
Durham	Birmingham	0	0	10	10
Warwick A	Imperial B	0	0	10	10
LSE A	Oxford A	0	0	10	10
Oxford B	Southampton B	10	0	0	10
Vassar B	Texas D	0	0	10	10